Patient interface with a seal-forming structure having varying thickness

ABSTRACT

A cushion assembly for a patient interface includes an elastomeric seal-forming portion that includes a dome-shaped superior region ( 3180 A); a saddle-shaped inferior region ( 3180 G); a first support region ( 3180 E) having a consistent wall thickness, preferably 2 mm, that is greater than the wall thickness of the dome-shaped superior and the saddle-shaped inferior regions, preferably 0.3 mm; a second support region ( 3180 D) having a varied wall thickness and is bounded by the first support region ( 3180 E) on a proximal side and having a distal side opposite the proximal side. In claim  1 , the wall thickness in the second support region ( 3180 D) increases from the distal side to the proximal side, preferably 2 to 1.3 mm. Preferably, wall thickness of a third support region ( 3180 F) is 1.3 mm, a compliant region ( 3180 C) is 0.85 mm and a flap ( 3180 H) is 0.5 mm. Preferably flap ( 3180 H) moves independently of a loop connection ( 3110 ).

This application is the U.S. national phase of International ApplicationNo. PCT/AU2016/050896 filed Sep. 23, 2016 which designated the U.S. andclaims priority U.S. Application No. 62/222,503 filed Sep. 23, 2015,International Application No. PCT/AU2016/050228 filed Mar. 24, 2016 andU.S. Application No. 62/377,217 filed Aug. 19, 2016, the entire contentsof each of which are incorporated herein by reference.

1 BACKGROUND OF THE TECHNOLOGY 1.1 Field of the Technology

The present technology relates to one or more of the detection,diagnosis, treatment, prevention and amelioration of respiratory-relateddisorders. The present technology also relates to medical devices orapparatus, and their use.

1.2 Description of the Related Art

1.2.1 Human Respiratory System and its Disorders

The respiratory system of the body facilitates gas exchange. The noseand mouth form the entrance to the airways of a patient.

The airways include a series of branching tubes, which become narrower,shorter and more numerous as they penetrate deeper into the lung. Theprime function of the lung is gas exchange, allowing oxygen to move fromthe inhaled air into the venous blood and carbon dioxide to move in theopposite direction. The trachea divides into right and left mainbronchi, which further divide eventually into terminal bronchioles. Thebronchi make up the conducting airways, and do not take part in gasexchange. Further divisions of the airways lead to the respiratorybronchioles, and eventually to the alveoli. The alveolated region of thelung is where the gas exchange takes place, and is referred to as therespiratory zone. See “Respiratory Physiology”, by John B. West,Lippincott Williams & Wilkins, 9th edition published 2012.

A range of respiratory disorders exist. Certain disorders may becharacterised by particular events, e.g. apneas, hypopneas, andhyperpneas.

Examples of respiratory disorders include Obstructive Sleep Apnea (OSA),Cheyne-Stokes Respiration (CSR), respiratory insufficiency, ObesityHyperventilation Syndrome (OHS), Chronic Obstructive Pulmonary Disease(COPD), Neuromuscular Disease (NMD) and Chest wall disorders.

Obstructive Sleep Apnea (OSA), a form of Sleep Disordered Breathing(SDB), is characterized by events including occlusion or obstruction ofthe upper air passage during sleep. It results from a combination of anabnormally small upper airway and the normal loss of muscle tone in theregion of the tongue, soft palate and posterior oropharyngeal wallduring sleep. The condition causes the affected patient to stopbreathing for periods typically of 30 to 120 seconds in duration,sometimes 200 to 300 times per night. It often causes excessive daytimesomnolence, and it may cause cardiovascular disease and brain damage.The syndrome is a common disorder, particularly in middle agedoverweight males, although a person affected may have no awareness ofthe problem. See U.S. Pat. No. 4,944,310 (Sullivan).

Cheyne-Stokes Respiration (CSR) is another form of sleep disorderedbreathing. CSR is a disorder of a patient's respiratory controller inwhich there are rhythmic alternating periods of waxing and waningventilation known as CSR cycles. CSR is characterised by repetitivede-oxygenation and re-oxygenation of the arterial blood. It is possiblethat CSR is harmful because of the repetitive hypoxia. In some patientsCSR is associated with repetitive arousal from sleep, which causessevere sleep disruption, increased sympathetic activity, and increasedafterload. See U.S. Pat. No. 6,532,959 (Berthon-Jones).

Respiratory failure is an umbrella term for respiratory disorders inwhich the lungs are unable to inspire sufficient oxygen or exhalesufficient CO₂ to meet the patient's needs. Respiratory failure mayencompass some or all of the following disorders.

A patient with respiratory insufficiency (a form of respiratory failure)may experience abnormal shortness of breath on exercise.

Obesity Hyperventilation Syndrome (OHS) is defined as the combination ofsevere obesity and awake chronic hypercapnia, in the absence of otherknown causes for hypoventilation. Symptoms include dyspnea, morningheadache and excessive daytime sleepiness.

Chronic Obstructive Pulmonary Disease (COPD) encompasses any of a groupof lower airway diseases that have certain characteristics in common.These include increased resistance to air movement, extended expiratoryphase of respiration, and loss of the normal elasticity of the lung.Examples of COPD are emphysema and chronic bronchitis. COPD is caused bychronic tobacco smoking (primary risk factor), occupational exposures,air pollution and genetic factors. Symptoms include: dyspnea onexertion, chronic cough and sputum production.

Neuromuscular Disease (NMD) is a broad term that encompasses manydiseases and ailments that impair the functioning of the muscles eitherdirectly via intrinsic muscle pathology, or indirectly via nervepathology. Some NMD patients are characterised by progressive muscularimpairment leading to loss of ambulation, being wheelchair-bound,swallowing difficulties, respiratory muscle weakness and, eventually,death from respiratory failure. Neuromuscular disorders can be dividedinto rapidly progressive and slowly progressive: (i) Rapidly progressivedisorders: Characterised by muscle impairment that worsens over monthsand results in death within a few years (e.g. Amyotrophic lateralsclerosis (ALS) and Duchenne muscular dystrophy (DMD) in teenagers);(ii) Variable or slowly progressive disorders: Characterised by muscleimpairment that worsens over years and only mildly reduces lifeexpectancy (e.g. Limb girdle, Facioscapulohumeral and Myotonic musculardystrophy). Symptoms of respiratory failure in NMD include: increasinggeneralised weakness, dysphagia, dyspnea on exertion and at rest,fatigue, sleepiness, morning headache, and difficulties withconcentration and mood changes.

Chest wall disorders are a group of thoracic deformities that result ininefficient coupling between the respiratory muscles and the thoraciccage. The disorders are usually characterised by a restrictive defectand share the potential of long term hypercapnic respiratory failure.Scoliosis and/or kyphoscoliosis may cause severe respiratory failure.Symptoms of respiratory failure include: dyspnea on exertion, peripheraloedema, orthopnea, repeated chest infections, morning headaches,fatigue, poor sleep quality and loss of appetite.

A range of therapies have been used to treat or ameliorate suchconditions. Furthermore, otherwise healthy individuals may takeadvantage of such therapies to prevent respiratory disorders fromarising. However, these have a number of shortcomings.

1.2.2 Therapy

Various therapies, such as Continuous Positive Airway Pressure (CPAP)therapy, Non-invasive ventilation (NIV) and Invasive ventilation (IV)have been used to treat one or more of the above respiratory disorders.

Continuous Positive Airway Pressure (CPAP) therapy has been used totreat Obstructive Sleep Apnea (OSA). The mechanism of action is thatcontinuous positive airway pressure acts as a pneumatic splint and mayprevent upper airway occlusion, such as by pushing the soft palate andtongue forward and away from the posterior oropharyngeal wall. Treatmentof OSA by CPAP therapy may be voluntary, and hence patients may electnot to comply with therapy if they find devices used to provide suchtherapy one or more of: uncomfortable, difficult to use, expensive andaesthetically unappealing.

Non-invasive ventilation (NIV) provides ventilatory support to a patientthrough the upper airways to assist the patient breathing and/ormaintain adequate oxygen levels in the body by doing some or all of thework of breathing. The ventilatory support is provided via anon-invasive patient interface. NIV has been used to treat CSR andrespiratory failure, in forms such as OHS, COPD, NMD and Chest Walldisorders. In some forms, the comfort and effectiveness of thesetherapies may be improved.

Invasive ventilation (IV) provides ventilatory support to patients thatare no longer able to effectively breathe themselves and may be providedusing a tracheostomy tube. In some forms, the comfort and effectivenessof these therapies may be improved.

1.2.3 Treatment Systems

These therapies may be provided by a treatment system or device. Suchsystems and devices may also be used to diagnose a condition withouttreating it.

A treatment system may comprise a Respiratory Pressure Therapy Device(RPT device), an air circuit, a humidifier, a patient interface, anddata management.

Another form of treatment system is a mandibular repositioning device.

1.2.3.1 Patient Interface

A patient interface may be used to interface respiratory equipment toits wearer, for example by providing a flow of air to an entrance to theairways. The flow of air may be provided via a mask to the nose and/ormouth, a tube to the mouth or a tracheostomy tube to the trachea of apatient. Depending upon the therapy to be applied, the patient interfacemay form a seal, e.g., with a region of the patient's face, tofacilitate the delivery of gas at a pressure at sufficient variance withambient pressure to effect therapy, e.g., at a positive pressure ofabout 10 cmH₂O relative to ambient pressure. For other forms of therapy,such as the delivery of oxygen, the patient interface may not include aseal sufficient to facilitate delivery to the airways of a supply of gasat a positive pressure of about 10 cmH₂O.

Certain other mask systems may be functionally unsuitable for thepresent field. For example, purely ornamental masks may be unable tomaintain a suitable pressure. Mask systems used for underwater swimmingor diving may be configured to guard against ingress of water from anexternal higher pressure, but not to maintain air internally at a higherpressure than ambient.

Certain masks may be clinically unfavourable for the present technologye.g. if they block airflow via the nose and only allow it via the mouth.

Certain masks may be uncomfortable or impractical for the presenttechnology if they require a patient to insert a portion of a maskstructure in their mouth to create and maintain a seal via their lips.

Certain masks may be impractical for use while sleeping, e.g. forsleeping while lying on one's side in bed with a head on a pillow.

The design of a patient interface presents a number of challenges. Theface has a complex three-dimensional shape. The size and shape of nosesand heads varies considerably between individuals. Since the headincludes bone, cartilage and soft tissue, different regions of the facerespond differently to mechanical forces. The jaw or mandible may moverelative to other bones of the skull. The whole head may move during thecourse of a period of respiratory therapy.

As a consequence of these challenges, some masks suffer from being oneor more of obtrusive, aesthetically undesirable, costly, poorly fitting,difficult to use, and uncomfortable especially when worn for longperiods of time or when a patient is unfamiliar with a system. Wronglysized masks can give rise to reduced compliance, reduced comfort andpoorer patient outcomes. Masks designed solely for aviators, masksdesigned as part of personal protection equipment (e.g. filter masks),SCUBA masks, or for the administration of anaesthetics may be tolerablefor their original application, but nevertheless such masks may beundesirably uncomfortable to be worn for extended periods of time, e.g.,several hours. This discomfort may lead to a reduction in patientcompliance with therapy. This is even more so if the mask is to be wornduring sleep.

CPAP therapy is highly effective to treat certain respiratory disorders,provided patients comply with therapy. If a mask is uncomfortable, ordifficult to use a patient may not comply with therapy. Since it isoften recommended that a patient regularly wash their mask, if a mask isdifficult to clean (e.g., difficult to assemble or disassemble),patients may not clean their mask and this may impact on patientcompliance.

While a mask for other applications (e.g. aviators) may not be suitablefor use in treating sleep disordered breathing, a mask designed for usein treating sleep disordered breathing may be suitable for otherapplications.

For these reasons, patient interfaces for delivery of CPAP during sleepform a distinct field.

1.2.3.1.1 Seal-Forming Portion

Patient interfaces may include a seal-forming portion. Since it is indirect contact with the patient's face, the shape and configuration ofthe seal-forming portion can have a direct impact the effectiveness andcomfort of the patient interface.

A patient interface may be partly characterised according to the designintent of where the seal-forming portion is to engage with the face inuse. In one form of patient interface, a seal-forming portion maycomprise a first sub-portion to form a seal around the left naris and asecond sub-portion to form a seal around the right naris. In one form ofpatient interface, a seal-forming portion may comprise a single elementthat surrounds both nares in use. Such single element may be designed tofor example overlay an upper lip region and a nasal bridge region of aface. In one form of patient interface a seal-forming portion maycomprise an element that surrounds a mouth region in use, e.g. byforming a seal on a lower lip region of a face. In one form of patientinterface, a seal-forming portion may comprise a single element thatsurrounds both nares and a mouth region in use. These different types ofpatient interfaces may be known by a variety of names by theirmanufacturer including nasal masks, full-face masks, nasal pillows,nasal puffs and oro-nasal masks.

A seal-forming portion that may be effective in one region of apatient's face may be inappropriate in another region, e.g. because ofthe different shape, structure, variability and sensitivity regions ofthe patient's face. For example, a seal on swimming goggles thatoverlays a patient's forehead may not be appropriate to use on apatient's nose.

Certain seal-forming portions may be designed for mass manufacture suchthat one design fit and be comfortable and effective for a wide range ofdifferent face shapes and sizes. To the extent to which there is amismatch between the shape of the patient's face, and the seal-formingportion of the mass-manufactured patient interface, one or both mustadapt in order for a seal to form.

One type of seal-forming portion extends around the periphery of thepatient interface, and is intended to seal against the patient's facewhen force is applied to the patient interface with the seal-formingportion in confronting engagement with the patient's face. Theseal-forming portion may include an air or fluid filled cushion, or amoulded or formed surface of a resilient seal element made of anelastomer such as a rubber. With this type of seal-forming portion, ifthe fit is not adequate, there will be gaps between the seal-formingportion and the face, and additional force will be required to force thepatient interface against the face in order to achieve a seal.

Another type of seal-forming portion incorporates a flap seal of thinmaterial positioned about the periphery of the mask so as to provide aself-sealing action against the face of the patient when positivepressure is applied within the mask Like the previous style of sealforming portion, if the match between the face and the mask is not good,additional force may be required to achieve a seal, or the mask mayleak. Furthermore, if the shape of the seal-forming portion does notmatch that of the patient, it may crease or buckle in use, giving riseto leaks.

Another type of seal-forming portion may comprise a friction-fitelement, e.g. for insertion into a naris, however some patients findthese uncomfortable.

Another form of seal-forming portion may use adhesive to achieve a seal.Some patients may find it inconvenient to constantly apply and remove anadhesive to their face.

A range of patient interface seal-forming portion technologies aredisclosed in the following patent applications, assigned to ResMedLimited: WO 1998/004,310; WO 2006/074,513; WO 2010/135,785.

One form of nasal pillow is found in the Adam Circuit manufactured byPuritan Bennett. Another nasal pillow, or nasal puff is the subject ofU.S. Pat. No. 4,782,832 (Trimble et al.), assigned to Puritan-BennettCorporation.

ResMed Limited has manufactured the following products that incorporatenasal pillows: SWIFT™ nasal pillows mask, SWIFT™ II nasal pillows mask,SWIFT™ LT nasal pillows mask, SWIFT™ FX nasal pillows mask and MIRAGELIBERTY™ full-face mask. The following patent applications, assigned toResMed Limited, describe examples of nasal pillows masks: InternationalPatent Application WO2004/073,778 (describing amongst other thingsaspects of the ResMed Limited SWIFT™ nasal pillows), US PatentApplication 2009/0044808 (describing amongst other things aspects of theResMed Limited SWIFT™ LT nasal pillows); International PatentApplications WO 2005/063,328 and WO 2006/130,903 (describing amongstother things aspects of the ResMed Limited MIRAGE LIBERTY™ full-facemask); International Patent Application WO 2009/052,560 (describingamongst other things aspects of the ResMed Limited SWIFT™ FX nasalpillows).

1.2.3.1.2 Positioning and Stabilising

A seal-forming portion of a patient interface used for positive airpressure therapy is subject to the corresponding force of the airpressure to disrupt a seal. Thus a variety of techniques have been usedto position the seal-forming portion, and to maintain it in sealingrelation with the appropriate portion of the face.

One technique is the use of adhesives. See for example US PatentApplication Publication No. US 2010/0000534. However, the use ofadhesives may be uncomfortable for some.

Another technique is the use of one or more straps and/or stabilisingharnesses. Many such harnesses suffer from being one or more ofill-fitting, bulky, uncomfortable and awkward to use.

1.2.3.2 Respiratory Pressure Therapy (RPT) Device

A respiratory pressure therapy (RPT) device may be used to deliver oneor more of a number of therapies described above, such as by generatinga flow of air for delivery to an entrance to the airways. The flow ofair may be pressurised. Examples of RPT devices include a CPAP deviceand a ventilator.

Air pressure generators are known in a range of applications, e.g.industrial-scale ventilation systems. However, air pressure generatorsfor medical applications have particular requirements not fulfilled bymore generalised air pressure generators, such as the reliability, sizeand weight requirements of medical devices. In addition, even devicesdesigned for medical treatment may suffer from shortcomings, pertainingto one or more of: comfort, noise, ease of use, efficacy, size, weight,manufacturability, cost, and reliability.

An example of the special requirements of certain RPT devices isacoustic noise.

Table of noise output levels of prior RPT devices (one specimen only,measured using test method specified in ISO 3744 in CPAP mode at 10cmH₂O).

A-weighted sound Year RPT Device name pressure level dB(A) (approx.)C-Series Tango ™ 31.9 2007 C-Series Tango ™ with Humidifier 33.1 2007 S8Escape ™ II 30.5 2005 S8 Escape ™ II with H4i ™ Humidifier 31.1 2005 S9AutoSet ™ 26.5 2010 S9 AutoSet ™ with H5i Humidifier 28.6 2010

One known RPT device used for treating sleep disordered breathing is theS9 Sleep Therapy System, manufactured by ResMed Limited. Another exampleof an RPT device is a ventilator. Ventilators such as the ResMedStellar™ Series of Adult and Paediatric Ventilators may provide supportfor invasive and non-invasive non-dependent ventilation for a range ofpatients for treating a number of conditions such as but not limited toNMD, OHS and COPD.

The ResMed Elisée™ 150 ventilator and ResMed VS III™ ventilator mayprovide support for invasive and non-invasive dependent ventilationsuitable for adult or paediatric patients for treating a number ofconditions. These ventilators provide volumetric and barometricventilation modes with a single or double limb circuit. RPT devicestypically comprise a pressure generator, such as a motor-driven bloweror a compressed gas reservoir, and are configured to supply a flow ofair to the airway of a patient. In some cases, the flow of air may besupplied to the airway of the patient at positive pressure. The outletof the RPT device is connected via an air circuit to a patient interfacesuch as those described above.

The designer of a device may be presented with an infinite number ofchoices to make. Design criteria often conflict, meaning that certaindesign choices are far from routine or inevitable. Furthermore, thecomfort and efficacy of certain aspects may be highly sensitive tosmall, subtle changes in one or more parameters.

1.2.3.3 Humidifier

Delivery of a flow of air without humidification may cause drying ofairways. The use of a humidifier with an RPT device and the patientinterface produces humidified gas that minimizes drying of the nasalmucosa and increases patient airway comfort. In addition in coolerclimates, warm air applied generally to the face area in and about thepatient interface is more comfortable than cold air.

A range of artificial humidification devices and systems are known,however they may not fulfil the specialised requirements of a medicalhumidifier.

Medical humidifiers are used to increase humidity and/or temperature ofthe flow of air in relation to ambient air when required, typicallywhere the patient may be asleep or resting (e.g. at a hospital). Amedical humidifier for bedside placement may be small. A medicalhumidifier may be configured to only humidify and/or heat the flow ofair delivered to the patient without humidifying and/or heating thepatient's surroundings. Room-based systems (e.g. a sauna, an airconditioner, or an evaporative cooler), for example, may also humidifyair that is breathed in by the patient, however those systems would alsohumidify and/or heat the entire room, which may cause discomfort to theoccupants. Furthermore medical humidifiers may have more stringentsafety constraints than industrial humidifiers

While a number of medical humidifiers are known, they can suffer fromone or more shortcomings. Some medical humidifiers may provideinadequate humidification, some are difficult or inconvenient to use bypatients.

1.2.3.4 Data Management

There may be clinical reasons to obtain data to determine whether thepatient prescribed with respiratory therapy has been “compliant”, e.g.that the patient has used their RPT device according to certain a“compliance rule”. One example of a compliance rule for CPAP therapy isthat a patient, in order to be deemed compliant, is required to use theRPT device for at least four hours a night for at least 21 of 30consecutive days. In order to determine a patient's compliance, aprovider of the RPT device, such as a health care provider, may manuallyobtain data describing the patient's therapy using the RPT device,calculate the usage over a predetermined time period, and compare withthe compliance rule. Once the health care provider has determined thatthe patient has used their RPT device according to the compliance rule,the health care provider may notify a third party that the patient iscompliant.

There may be other aspects of a patient's therapy that would benefitfrom communication of therapy data to a third party or external system.

Existing processes to communicate and manage such data can be one ormore of costly, time-consuming, and error-prone.

1.2.3.5 Mandibular Repositioning

A mandibular repositioning device (MRD) or mandibular advancement device(MAD) is one of the treatment options for sleep apnea and snoring. It isan adjustable oral appliance available from a dentist or other supplierthat holds the lower jaw (mandible) in a forward position during sleep.The MRD is a removable device that a patient inserts into their mouthprior to going to sleep and removes following sleep. Thus, the MRD isnot designed to be worn all of the time. The MRD may be custom made orproduced in a standard form and includes a bite impression portiondesigned to allow fitting to a patient's teeth. This mechanicalprotrusion of the lower jaw expands the space behind the tongue, putstension on the pharyngeal walls to reduce collapse of the airway anddiminishes palate vibration.

In certain examples a mandibular advancement device may comprise anupper splint that is intended to engage with or fit over teeth on theupper jaw or maxilla and a lower splint that is intended to engage withor fit over teeth on the upper jaw or mandible. The upper and lowersplints are connected together laterally via a pair of connecting rods.The pair of connecting rods are fixed symmetrically on the upper splintand on the lower splint.

In such a design the length of the connecting rods is selected such thatwhen the MRD is placed in a patient's mouth the mandible is held in anadvanced position. The length of the connecting rods may be adjusted tochange the level of protrusion of the mandible. A dentist may determinea level of protrusion for the mandible that will determine the length ofthe connecting rods.

Some MRDs are structured to push the mandible forward relative to themaxilla while other MADs, such as the ResMed Narval CC™ MRD are designedto retain the mandible in a forward position. This device also reducesor minimises dental and temporo-mandibular joint (TMJ) side effects.Thus, it is configured to minimises or prevent any movement of one ormore of the teeth.

1.2.3.6 Vent Technologies

Some forms of treatment systems may include a vent to allow the washoutof exhaled carbon dioxide. The vent may allow a flow of gas from aninterior space of a patient interface, e.g., the plenum chamber, to anexterior of the patient interface, e.g., to ambient.

The vent may comprise an orifice and gas may flow through the orifice inuse of the mask. Many such vents are noisy. Others may become blocked inuse and thus provide insufficient washout. Some vents may be disruptiveof the sleep of a bed partner 1100 of the patient 1000, e.g. throughnoise or focussed airflow.

ResMed Limited has developed a number of improved mask venttechnologies. See International Patent Application Publication No. WO1998/034,665; International Patent Application Publication No. WO2000/078,381; U.S. Pat. No. 6,581,594; US Patent Application PublicationNo. US 2009/0050156; US Patent Application Publication No. 2009/0044808.

Table of noise of prior masks (ISO 17510-2:2007, 10 cmH₂O pressure at 1m)

A-weighted A-weighted sound power sound pressure level dB(A) dB(A) YearMask name Mask type (uncertainty) (uncertainty) (approx.) Glue-on (*)nasal 50.9 42.9 1981 ResCare nasal 31.5 23.5 1993 standard (*) ResMednasal 29.5 21.5 1998 Mirage ™ (*) ResMed nasal 36 (3) 28 (3) 2000UltraMirage ™ ResMed nasal 32 (3) 24 (3) 2002 Mirage Activa ™ ResMednasal 30 (3) 22 (3) 2008 Mirage Micro ™ ResMed nasal 29 (3) 22 (3) 2008Mirage ™ SoftGel ResMed nasal 26 (3) 18 (3) 2010 Mirage ™ FX ResMednasal pillows 37 29 2004 Mirage Swift ™ (*) ResMed nasal pillows 28 (3)20 (3) 2005 Mirage Swift ™ II ResMed nasal pillows 25 (3) 17 (3) 2008Mirage Swift ™ LT ResMed AirFit nasal pillows 21(3) 13 (3) 2014 P10 (*one specimen only, measured using test method specified in ISO 3744 inCPAP mode at 10 cmH₂O)Sound pressure values of a variety of objects arelisted below

A-weighted sound Object pressure dB(A) Notes Vacuum cleaner: Nilfisk 68ISO 3744 at 1 m Walter Broadly Litter Hog: B+ distance GradeConversational speech 60 1 m distance Average home 50 Quiet library 40Quiet bedroom at night 30 Background in TV studio 201.2.4 Diagnosis and Monitoring Systems

Polysomnography (PSG) is a conventional system for diagnosis andmonitoring of cardio-pulmonary disorders, and typically involves expertclinical staff to apply the system. PSG typically involves the placementof 15 to 20 contact sensors on a patient in order to record variousbodily signals such as electroencephalography (EEG), electrocardiography(ECG), electrooculograpy (EOG), electromyography (EMG), etc. PSG forsleep disordered breathing has involved two nights of observation of apatient in a clinic, one night of pure diagnosis and a second night oftitration of treatment parameters by a clinician. PSG is thereforeexpensive and inconvenient. In particular it is unsuitable for homesleep testing.

Clinical experts may be able to diagnose or monitor patients adequatelybased on visual observation of PSG signals. However, there arecircumstances where a clinical expert may not be available, or aclinical expert may not be affordable. Different clinical experts maydisagree on a patient's condition. In addition, a given clinical expertmay apply a different standard at different times.

2 BRIEF SUMMARY OF THE TECHNOLOGY

The present technology is directed towards providing medical devicesused in the diagnosis, amelioration, treatment, or prevention ofrespiratory disorders having one or more of improved comfort, cost,efficacy, ease of use and manufacturability.

A first aspect of the present technology relates to apparatus used inthe diagnosis, amelioration, treatment or prevention of a respiratorydisorder.

Another aspect of the present technology relates to methods used in thediagnosis, amelioration, treatment or prevention of a respiratorydisorder.

An aspect of certain forms of the present technology is to providemethods and/or apparatus that improve the compliance of patients withrespiratory therapy.

One aspect of the present technology is directed to a patient interfacethat comprises: a plenum chamber pressurisable to a therapeutic pressureof at least 6cmH2O above ambient air pressure, said plenum chamberincluding a plenum chamber inlet port, said plenum chamber inlet portbeing sized and structured to receive a flow of air at the therapeuticpressure for breathing by a patient; a sealing structure constructed andarranged to have a shape to form a seal with a region of the patient'sface surrounding an entrance to the patient's airways such that the flowof air at said therapeutic pressure is delivered to at least an entranceto the patient's nares, said seal being formed to prevent air exitingfrom the plenum chamber between the sealing structure and said region ofthe patient's face, the sealing structure structured and arranged tomaintain said therapeutic pressure in the plenum chamber throughout thepatient's respiratory cycle in use; a positioning and stabilisingstructure to maintain the sealing structure in a therapeuticallyeffective position on the patient's head while the patient is lying in aside sleeping position and while the patient is lying in a supinesleeping position said positioning and stabilising structure including alow-profile side portion and a low-profile rear portion; and a washoutvent structure configured to allow a continuous vent flow from aninterior of the plenum chamber to ambient whilst the pressure within theplenum chamber is positive with respect to ambient, said vent structurebeing configured such that the vent flow rate has a magnitude sufficientto help reduce rebreathing of exhaled CO2 by the patient during bothpatient inhalation and patient exhalation while maintaining thetherapeutic pressure in the plenum chamber in use, wherein the sealingstructure comprises a sealing surface that forms the seal against thepatient's face in use, wherein the sealing structure comprises a tiethat extends between a first interior surface region of the sealingstructure that is opposite the sealing surface and a second interiorsurface region of the patient interface such that the tie resistsdeformation of the sealing structure.

In examples, (a) the sealing structure may comprise the second interiorsurface region, the second interior surface region being spaced from thefirst interior surface region, (b) the plenum chamber may comprise thesecond interior surface region, the second interior surface region beingspaced from the first interior surface region, (c) the tie and thesealing structure may comprise a unitary structure formed from ahomogeneous material, (d) the homogeneous material may be siliconerubber, (e) the silicone rubber may be liquid silicone rubber orcompression molded silicone rubber, (f) the sealing structure maycomprises a sealing flap at an edge region, the sealing flap beingshaped and positioned to seal at least against a side of the patient'snose in use, and the sealing flap being thinner than adjacent regions ofthe sealing structure, (g) the first interior surface region may beadjacent to the sealing flap such that the tie is spaced inwardly fromthe sealing flap, (h) the tie may extend contiguously from the sealingstructure at an edge region such that the tie forms an extension of thesealing surface, (i) the tie may comprise an inner surface and thesealing structure may comprise an interior surface, (j) the innersurface of the tie being adjacent to and separated from the interiorsurface of the sealing structure, (k) the plenum chamber may beconstructed from a transparent material, (l) the patient interface maybe configured so that no part of the patient interface structure entersthe mouth in use, (m) the sealing structure may be configured so as tonot extend internally of the patient's airways in use, (n) the sealingstructure may be configured so as not to not extend below a mentalprotuberance region in use, and/or (o) the plenum chamber may beconfigured so as not to cover the eyes in use.

Another aspect of the present technology is directed to an assembly fora patient interface that comprises: a plenum chamber pressurisable to atherapeutic pressure of at least 6cmH2O above ambient air pressure, saidplenum chamber including a plenum chamber inlet port, said plenumchamber inlet port being sized and structured to receive a flow of airat the therapeutic pressure for breathing by a patient; and a sealingstructure constructed and arranged to have a shape to form a seal with aregion of the patient's face surrounding an entrance to the patient'sairways such that the flow of air at said therapeutic pressure isdelivered to at least an entrance to the patient's nares, said sealbeing formed to prevent air exiting from the plenum chamber between thesealing structure and said region of the patient's face, the sealingstructure structured and arranged to maintain said therapeutic pressurein the plenum chamber throughout the patient's respiratory cycle in use;wherein the sealing structure comprises a sealing surface that forms theseal against the patient's face in use, wherein the sealing structurecomprises a connecting portion that extends between a first interiorsurface region of the sealing structure that is opposite the sealingsurface and a second interior surface region of the assembly such thatthe connecting portion resists deformation of the sealing structure.

In examples, (a) the sealing structure may comprise the second interiorsurface region, the second interior surface region being spaced from thefirst interior surface region, (b) the plenum chamber may comprise thesecond interior surface region, the second interior surface region beingspaced from the first interior surface region, (c) the connectingportion and the sealing structure may comprise a unitary structureformed from a homogeneous material, (d) the homogeneous material may besilicone rubber, (e) the silicone rubber may liquid silicone rubber orcompression molded silicone rubber, (f) the sealing structure maycomprise a sealing flap at an edge region, the sealing flap being shapedand positioned to seal at least against a side of the patient's nose inuse, and the sealing flap being thinner than adjacent regions of thesealing structure, (g) the first interior surface region may be adjacentto the sealing flap such that the connecting portion is spaced inwardlyfrom the sealing flap, (h) the connecting portion may extendcontiguously from the sealing structure at an edge region such that theconnecting portion forms an extension of the sealing surface, (i) theconnecting portion may comprise an inner surface and the sealingstructure may comprise an interior surface, the inner surface of theconnecting portion being adjacent to and separated from the interiorsurface of the sealing structure, (j) the plenum chamber may beconstructed from a transparent material, (k) the assembly may beconfigured so that no part of the assembly enters the mouth in use, (l)the sealing structure may be configured so as to not extend internallyof the patient's airways in use, (m) the sealing structure may beconfigured so as not to not extend below a mental protuberance region inuse, and/or (n) the plenum chamber is configured so as not to cover theeyes in use.

One form of the present technology comprises a sealing structure to sealagainst a user's face around the user's airways. The sealing structureincludes a flap or membrane that extends inward towards the user'sairways and includes an attachment structure that prevents an innerboundary of the flap or membrane from being blown outwards (e.g., foldedbackwards upon itself) due to internal pressurization.

In examples, the attachment structure may comprise: one or moreribs/ties/connecting portions/connecting structures, a flap that extendsfrom the membrane and folds inwards and attaches to another structure toform a tube or loop, or a tube underlying and attached to the membrane.

Another aspect of one form of the present technology is a sealingstructure for a patient interface for sealed delivery of a flow of airat a continuously positive pressure with respect to ambient air pressureto an entrance to the patient's airways including at least entrance of apatient's nares. The patient interface is configured to maintain atherapy pressure in a range of about 3 cmH2O to about 40 cmH2O aboveambient air pressure in use, throughout the patient's respiratory cycle,while the patient is sleeping, to ameliorate sleep disordered breathing.The sealing structure comprises: a sealing surface configured to form aseal around a periphery of the entrance to the patient's airways, and aloop that folds the sealing structure inwards of an outer perimeter ofthe sealing structure to form a substantially tube-shaped structure sothat the loop is continuous, the loop comprising a portion of thesealing surface.

In examples, (a) the sealing structure further comprising a sealing flapprotruding towards an inner perimeter of the sealing structure, (b) thesealing flap is configured to form a seal against the sides of the noseabove the nasal bones of the patient, (c) the sealing flap is configuredto avoid sealing against the alar, (d) the portion of the sealingsurface has increased flexibility relative to a remaining portion of theloop the portion of the sealing surface comprises a thinner wall sectionthan a remaining portion of the loop, (e) the portion of the sealingsurface comprises a thicker wall section than a remaining portion of theloop, (f) the loop is located to contact the side wall of the noseincluding the alar, (g) the loop provides a continuous surfaceconfigured to maintain contact with the sides of the nose, above thenasal bones of the patient, (h) the loop comprises at least one closedend, (i) the loop folds the sealing structure inwards to form aconnection point on an inner surface of the sealing structure, (j) theconnection point is positioned relative to the sealing surface toprovide sufficient tension to the loop to counteract outward blowout ofthe sealing surface when the therapy pressure is applied to an interiorsurface of the loop, (k) the loop forms a predetermined angle at theconnection point and the predetermined angle determines tension in theloop when the therapy pressure is applied, (l) the connection point isadjustable, (m) the connection point is a releasable connection, (n) thesealing structure further comprising a second connection point (o) thesealing surface comprises a region of reduced friction to reduceadherence with the patient's face, (p) the region of reduced friction isa frosted surface, (q) the region of reduced friction is adapted toallow the sides of the nose of the patient to slide freely against thesealing surface, and/or (r) the loop provides an edgeless sealingsurface.

Another aspect of one form of the present technology is a patientinterface for sealed delivery of a flow of air at a continuouslypositive pressure with respect to ambient air pressure to an entrance tothe patient's airways including at least entrance of a patient's nares.The patient interface is configured to maintain a therapy pressure in arange of about 3 cmH2O to about 40 cmH2O above ambient air pressure inuse, throughout the patient's respiratory cycle, while the patient issleeping, to ameliorate sleep disordered breathing. The patientinterface comprises a sealing structure to seal the patient interfaceagainst the patient's face. The sealing structure comprises a sealingsurface configured to form a seal around a periphery of the entrance tothe patient's airways, and a loop that folds the sealing structureinwards of an outer perimeter of the sealing structure to form asubstantially tube-shaped structure so that the loop is continuous, theloop comprising a portion of the sealing surface. The patient interfacefurther comprises a positioning and stabilising structure to maintainthe sealing structure in sealing contact with an area surrounding anentrance to the patient's airways while maintaining a therapeuticpressure at the entrance to the patient's airways; a plenum chamberpressurised at a pressure above ambient pressure in use; and a gaswashout vent configured to allow a flow of patient exhaled CO2 to anexterior of the patient interface to minimise rebreathing of exhaled CO2by the patient.

In examples, (a) a sealing flap protrudes towards an inner perimeter ofthe sealing structure, (b) the sealing flap is configured to form a sealagainst the sides of the nose above the nasal bones and adjacent thesides of the nose above the maxilla, in the depression adjacent theendocanthion of the patient, (c) the sealing flap is configured to avoidsealing against the alar, (d) the portion of the sealing surface hasincreased flexibility relative to a remaining portion of the loop, (e)the portion of the sealing surface comprises a thinner wall section thana remaining portion of the loop, (f) the portion of the sealing surfacecomprises a thicker wall section than a remaining portion of the loop,(g) the sealing surface comprises a region of reduced friction to reduceadherence with the patient's face, (h) the region of reduced friction isa frosted surface, (i) the region of reduced friction is adapted toallow the sides of the nose of the patient to slide freely against thesealing surface, (j) the first loop defines an area of the sealingstructure adapted to contact the patient's face, (k) the first portionand the second portion are part of the area of the sealing structureadapted to contact the patient's face, (l) the first loop is continuous,(m) the second loop is located to contact or be alongside the patient'snose, (n) the second loop is located so that the substantiallytube-shaped structure is adapted to contact or be located alongside thepatient's nose, (o) the substantially tube-shaped structure is adaptedto be located substantially parallel to a side of the patient's nose,(p) the sealing structure further comprises a second one of the secondloop, (g) the substantially tube-shaped structure comprises a hollowinterior that is adapted to be in fluid communication with the pressureabove ambient pressure, (r) the substantially tube-shaped structurecomprises two open ends, and/or (s) the second loop is adapted toprevent the second loop from a blowout when the patient interface isinternally pressurized and adjusted by the patient.

Another aspect of one form of the present technology is a patientinterface for sealed delivery of a flow of air at a continuouslypositive pressure with respect to ambient air pressure to an entrance tothe patient's airways including at least entrance of a patient's nares,wherein the patient interface is configured to maintain a therapypressure in a range of about 3 cmH2O to about 40 cmH2O above ambient airpressure in use, throughout the patient's respiratory cycle, while thepatient is sleeping, to ameliorate sleep disordered breathing. Thepatient interface comprises a sealing structure to seal the patientinterface against the patient's face. The sealing structure comprises aface contacting portion adapted to contact around a periphery of theentrance to the patient's airways, and at least a first substantiallycylindrical region that has an uninterrupted circumference, wherein aportion of the cylindrical region comprises a portion of the facecontacting portion. The patient interface further comprises apositioning and stabilising structure to maintain the sealing structurein sealing contact with an area surrounding an entrance to the patient'sairways while maintaining a therapeutic pressure at the entrance to thepatient's airways; a plenum chamber pressurised at a pressure aboveambient pressure in use; and a gas washout vent configured to allow aflow of patient exhaled CO2 to an exterior of the patient interface tominimise rebreathing of exhaled CO2 by the patient.

In examples, (a) the sealing structure comprises unrestrained edgesadjacent to ends of the first substantially cylindrical region, (b) thesealing structure comprises an unrestrained edge all around theperiphery of the entrance to the patient's airways except at the firstsubstantially cylindrical region, (c) the portion of the face contactingportion forms a convex surface adapted to contact the patient's face,(d) the first substantially cylindrical region is located to contact orbe alongside the patient's ala, (e) the first substantially cylindricalregion is located to be substantially parallel to the patient's ala, (f)the patient interface further comprises a second one of the cylindricalregion, (g) the cylindrical region comprises a second substantiallycylindrical region that has a second uninterrupted circumference,wherein a portion of the second cylindrical region comprises a secondportion of the face contacting portion, (h) wherein the firstsubstantially cylindrical region comprises a hollow interior that isadapted to be in fluid communication with the pressure above ambientpressure, (i) the first substantially cylindrical region comprises twoopen ends, and/or (j) the first substantially cylindrical region isadapted to prevent the face contacting portion from a blowout when thepatient interface is internally pressurized and adjusted by the patient.

Another aspect of one form of the present technology is a patientinterface for sealed delivery of a flow of air at a continuouslypositive pressure with respect to ambient air pressure to an entrance tothe patient's airways including at least entrance of a patient's nares,wherein the patient interface is configured to maintain a therapypressure in a range of about 3 cmH2O to about 40 cmH2O above ambient airpressure in use, throughout the patient's respiratory cycle, while thepatient is sleeping, to ameliorate sleep disordered breathing. Thepatient interface comprises a sealing structure comprising materialfolded upon itself to form an uninterrupted tubular shape, where only aportion of a circumference of the tubular shape is configured to contactthe patient's face; a positioning and stabilising structure to maintainthe sealing structure in sealing contact with an area surrounding anentrance to the patient's airways while maintaining a therapeuticpressure at the entrance to the patient's airways; a plenum chamberpressurised at a pressure above ambient pressure in use; and a gaswashout vent configured to allow a flow of patient exhaled CO2 to anexterior of the patient interface to minimise rebreathing of exhaled CO2by the patient, wherein an interior of the tubular shape is adapted tobe in fluid communication with the pressure above ambient pressure.

In examples, (a) the uninterrupted tubular shape has an interior surfaceof the tube and an exterior surface of the tube, the interior surface ofthe tube is adapted to be exposed to the pressure above ambient pressurein use, a first portion of the exterior surface of the tube is adaptedto be exposed to ambient pressure in use, and a second portion of theexterior surface of the tube is adapted to be exposed to the pressureabove ambient pressure in use, (b) the sealing structure furthercomprises a surface that contacts around a periphery of the patient'sairways and the portion of the uninterrupted tubular shape is part ofthe surface, (c) the uninterrupted tubular shape is open on at least oneend, (d) the uninterrupted tubular shape is open on two ends, (e) theuninterrupted tubular shape is adapted to be alongside the patient'sala, (f) the uninterrupted tubular shape is adapted to contact thepatient's ala, (g) the material is folded to form a second uninterruptedtubular shape where only a portion of a circumference of the seconduninterrupted tubular shape is configured to contact the patient's face,(h) the uninterrupted tubular shapes are adapted to be on opposite sidesof the patient's nose, and/or (i) the uninterrupted tubular shape isadapted to prevent the material from a blowout when the patientinterface is internally pressurized and adjusted by the patient.

Another aspect of one form of the present technology is a patientinterface for sealed delivery of a flow of air at a continuouslypositive pressure with respect to ambient air pressure to an entrance tothe patient's airways including at least entrance of a patient's nares,wherein the patient interface is configured to maintain a therapypressure in a range of about 3 cmH2O to about 40 cmH2O above ambient airpressure in use, throughout the patient's respiratory cycle, while thepatient is sleeping, to ameliorate sleep disordered breathing. Thepatient interface comprises a sealing structure to seal the patientinterface against the patient's face. The sealing structure comprises afirst face contacting portion with an unconnected edge at an innerboundary of the sealing structure, a second face contacting portion thatis part of a tubular structure, and the first face contacting portionand the second face contacting portion each form part of a continuousmembrane that is configured to contact the patient's face around aperiphery of the entrance to the patient's airways. The patientinterface further comprises a positioning and stabilising structure tomaintain the sealing structure in sealing contact with an areasurrounding an entrance to the patient's airways while maintaining atherapeutic pressure at the entrance to the patient's airways; a plenumchamber pressurised at a pressure above ambient pressure in use; and agas washout vent configured to allow a flow of patient exhaled CO2 to anexterior of the patient interface to minimise rebreathing of exhaled CO2by the patient.

In examples, (a) the patient interface further comprises a plurality ofthe second face contacting portion, (b) the second face contactingportion is adapted to contact the patient's face adjacent to or on thepatient's ala, and/or (c) the tubular structure is adapted to preventthe continuous membrane from a blowout when the patient interface isinternally pressurized and adjusted by the patient.

Another aspect of one form of the present technology is a patientinterface for sealed delivery of a flow of air at a continuouslypositive pressure with respect to ambient air pressure to an entrance tothe patient's airways including at least entrance of a patient's nares,wherein the patient interface is configured to maintain a therapypressure in a range of about 3 cmH2O to about 40 cmH2O above ambient airpressure in use, throughout the patient's respiratory cycle, while thepatient is sleeping, to ameliorate sleep disordered breathing. Thepatient interface comprises a sealing structure to seal the patientinterface against the patient's face. The sealing structure comprises asealing membrane, and a flap attached on a first end to the sealingmembrane and attached on a second end to another structure to preventthe sealing membrane from blowing outward due to the therapy pressure.The patient interface further comprises a positioning and stabilisingstructure to maintain the sealing structure in sealing contact with anarea surrounding an entrance to the patient's airways while maintaininga therapeutic pressure at the entrance to the patient's airways; aplenum chamber pressurised at a pressure above ambient pressure in use;and a gas washout vent configured to allow a flow of patient exhaled CO2to an exterior of the patient interface to minimise rebreathing ofexhaled CO2 by the patient.

In examples, (a) the sealing membrane and the flap form part of atubular structure, and/or (b) the sealing membrane is adapted to contactall around a periphery of the entrance to the patient's airways and theflap is only provided for a portion of the periphery.

Another aspect of one form of the present technology is a patientinterface for sealed delivery of a flow of air at a continuouslypositive pressure with respect to ambient air pressure to an entrance tothe patient's airways including at least entrance of a patient's nares,wherein the patient interface is configured to maintain a therapypressure in a range of about 3 cmH2O to about 40 cmH2O above ambient airpressure in use, throughout the patient's respiratory cycle, while thepatient is sleeping, to ameliorate sleep disordered breathing. Thepatient interface comprises a sealing structure to seal the patientinterface against the patient's face. The sealing structure comprises asealing membrane adapted to contact the patient's face around aperiphery of the entrance to the patient's airways, and a cylindricalregion underlying and attached to the sealing membrane. The patientinterface further comprises a positioning and stabilising structure tomaintain the sealing structure in sealing contact with an areasurrounding an entrance to the patient's airways while maintaining atherapeutic pressure at the entrance to the patient's airways; a plenumchamber pressurised at a pressure above ambient pressure in use; and agas washout vent configured to allow a flow of patient exhaled CO2 to anexterior of the patient interface to minimise rebreathing of exhaled CO2by the patient.

In examples, (a) the cylindrical region is located adjacent to thepatient's ala, (b) the cylindrical region includes an axis that issubstantially parallel to the patient's ala, (c) the cylindrical regionis adapted to prevent the sealing membrane from blowing away from theentrance to the patient's airways when the plenum chamber is pressurizedat the pressure above ambient pressure, and/or (d) the sealing membraneincludes an unconnected edge all around a periphery of the entrance tothe patient's airways.

Another aspect of one form of the present technology is a patientinterface for sealed delivery of a flow of air at a continuouslypositive pressure with respect to ambient air pressure to an entrance tothe patient's airways including at least entrance of a patient's nares,wherein the patient interface is configured to maintain a therapypressure in a range of about 3 cmH2O to about 40 cmH2O above ambient airpressure in use, throughout the patient's respiratory cycle, while thepatient is sleeping, to ameliorate sleep disordered breathing. Thepatient interface comprises a sealing structure to seal the patientinterface against the patient's face. The sealing structure comprises asealing membrane comprising an interior surface and an exterior surfaceadapted to contact the patient's face around a periphery of the entranceto the patient's airways, and a rib underlying and attached to theinterior surface such that the rib resists deformation of the sealingmembrane when pressure is applied to the interior surface. The patientinterface further comprises a positioning and stabilising structure tomaintain the sealing structure in sealing contact with an areasurrounding an entrance to the patient's airways while maintaining atherapeutic pressure at the entrance to the patient's airways; a plenumchamber pressurised at a pressure above ambient pressure in use; and agas washout vent configured to allow a flow of patient exhaled CO2 to anexterior of the patient interface to minimise rebreathing of exhaled CO2by the patient.

In examples, (a) the exterior surface includes a convex portion, (b) theinterior surface has a concave portion, (c) the concave portion and theconvex portion are located directly opposite one another on the exteriorsurface and interior surface, respectively, and the rib is attached tothe interior surface at the concave portion, (d) the rib is readilycrushed by a forced applied to the patient interface to hold the patientinterface to the patient, (e) the patient interface further comprises aplurality of the rib, (f) the rib is adapted to be adjacent thepatient's nose, (g) the rib is adapted to prevent the sealing membranefrom a blowout when the patient interface is internally pressurized andadjusted by the patient, and/or (h) the rib is substantially orthogonalto the interior surface.

Another aspect of one form of the present technology is a cushionassembly for a patient interface for sealed delivery of a flow of air ata continuously positive pressure with respect to ambient air pressure toan entrance to the patient's airways including at least entrance of apatient's nares, wherein the patient interface is configured to maintaina therapy pressure in a range of about 4 cmH2O to about 30 cmH2O aboveambient air pressure in use, throughout the patient's respiratory cycle,while the patient is sleeping, to ameliorate sleep disordered breathing.The cushion assembly may include an elastomeric seal-forming portionshaped to be bisected by a sagittal plane that includes a line tangentto the elastomeric seal-forming portion at a superior tangent point andan inferior tangent point. The elastomeric seal-forming portion mayinclude a dome-shaped superior region that straddles the sagittal planein the vicinity of the superior tangent point and a saddle-shapedinferior region that straddles the sagittal plane and includes theinferior tangent point. The elastomeric seal-forming portion may alsoinclude a first support region extending from the saddle-shaped inferiorregion to the dome-shaped superior region, the first support regionhaving a consistent elastomeric wall thickness that is greater than theelastomeric wall thickness of the dome-shaped superior region and thesaddle-shaped inferior region. The elastomeric seal-forming portion mayfurther include a second support region adjacent the first supportregion that extends from the saddle-shaped inferior region to thedome-shaped superior region, the second support region being bounded bythe first support region on a proximal side and having a distal sideopposite the proximal side, the elastomeric wall thickness in the secondsupport region increases from the distal side to the proximal side.

Another aspect of one form of the present technology is a cushionassembly for a patient interface for sealed delivery of a flow of air ata continuously positive pressure with respect to ambient air pressure toan entrance to the patient's airways including at least entrance of apatient's nares, wherein the patient interface is configured to maintaina therapy pressure in a range of about 4 cmH2O to about 30 cmH2O aboveambient air pressure in use, throughout the patient's respiratory cycle,while the patient is sleeping, to ameliorate sleep disordered breathing.The cushion assembly may include an elastomeric seal-forming structureshaped to be bisected by a sagittal plane that includes a line tangentto the elastomeric seal-forming structure at a superior tangent pointand an inferior tangent point. The elastomeric seal-forming structuremay include a posterior central opening and an anterior central openingopposite the posterior central opening and may include a pluralityclosed path concentric to the posterior central opening. A dome-shapedsuperior region may straddle the sagittal plane in the vicinity of thesuperior tangent point, the dome-shaped superior region being positionedon the outermost closed path. A saddle-shaped superior region maystraddle the sagittal plane in the vicinity of the superior tangentpoint, the saddle-shaped superior region being positioned on the innermost closed path. A saddle-shaped inferior region may straddle thesagittal plane and may include the inferior tangent point, thesaddle-shaped inferior region being on both the innermost closed pathand the outermost closed path. An elastomeric wall thickness of theelastomeric seal-forming structure may be invariable along a portion ofthe outermost closed path extending from the saddle-shaped inferiorregion to the dome-shaped superior region. The elastomeric wallthickness of the elastomeric seal-forming structure may vary along aportion of the innermost closed path that extends from saddle-shapedinferior region to the saddle-shaped superior region.

Another aspect of one form of the present technology is a cushionassembly for a patient interface for sealed delivery of a flow of air ata continuously positive pressure with respect to ambient air pressure toan entrance to the patient's airways including at least entrance of apatient's nares, wherein the patient interface is configured to maintaina therapy pressure in a range of about 4 cmH2O to about 30 cmH2O aboveambient air pressure in use, throughout the patient's respiratory cycle,while the patient is sleeping, to ameliorate sleep disordered breathing.The cushion assembly may include an elastomeric seal-forming structurethat is shaped to be bisected by a sagittal plane that has a line thatis tangent to the elastomeric seal-forming structure at a superiortangent point and at an inferior tangent point. A first nasal bridgeregion of the elastomeric seal-forming structure may straddle thesagittal plane in the vicinity of the superior tangent point. A secondnasal bridge region of the elastomeric seal-forming structure maystraddle the sagittal plane in the vicinity of the superior tangentpoint and is configured to seal against the patient's nasal bridge whenthe cushion is mounted on the patient's face, the second nasal bridgeregion having a thinner elastomeric wall than the first nasal bridgeregion. A chin region of the elastomeric seal-forming structure maystraddle the sagittal plane and includes the inferior tangent point, thechin region being configured to engage the patient's chin when thecushion is mounted on the patient's face, the chin region having thesame elastomeric wall thickness as the first nasal bridge region. Afirst support region and a second support region may be positioned sideby side and both extend from the chin region to the first nasal bridgeregion, the first support region having a consistent elastomeric wallthickness, and the second support region having a varied elastomericwall thickness.

Another aspect of one form of the present technology is a patientinterface that is moulded or otherwise constructed with a perimetershape which is complementary to that of an intended wearer.

An aspect of one form of the present technology is a method ofmanufacturing apparatus.

An aspect of certain forms of the present technology is a medical devicethat is easy to use, e.g. by a person who does not have medicaltraining, by a person who has limited dexterity, vision or by a personwith limited experience in using this type of medical device.

An aspect of one form of the present technology is a portable RPT devicethat may be carried by a person, e.g., around the home of the person.

An aspect of one form of the present technology is a patient interfacethat may be washed in a home of a patient, e.g., in soapy water, withoutrequiring specialised cleaning equipment. An aspect of one form of thepresent technology is a humidifier tank that may be washed in a home ofa patient, e.g., in soapy water, without requiring specialised cleaningequipment.

The methods, systems, devices and apparatus described herein can provideimproved functioning in a processor, such as of a processor of aspecific purpose computer, respiratory monitor and/or a respiratorytherapy apparatus. Moreover, the described methods, systems, devices andapparatus can provide improvements in the technological field ofautomated management, monitoring and/or treatment of respiratoryconditions, including, for example, sleep disordered breathing.

Of course, portions of the aspects may form sub-aspects of the presenttechnology. Also, various ones of the sub-aspects and/or aspects may becombined in various manners and also constitute additional aspects orsub-aspects of the present technology.

Other features of the technology will be apparent from consideration ofthe information contained in the following detailed description,abstract, drawings and claims.

3 BRIEF DESCRIPTION OF THE DRAWINGS

The present technology is illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawings, in whichlike reference numerals refer to similar elements including:

3.1 Treatment Systems

FIG. 1A shows a system including a patient 1000 wearing a patientinterface 3000, in the form of nasal pillows, receiving a supply of airat positive pressure from an RPT device 4000. Air from the RPT device4000 is humidified in a humidifier 5000, and passes along an air circuit4170 to the patient 1000. A bed partner 1100 is also shown. The patientis sleeping in a supine sleeping position.

FIG. 1B shows a system including a patient 1000 wearing a patientinterface 3000, in the form of a nasal mask, receiving a supply of airat positive pressure from an RPT device 4000. Air from the RPT device ishumidified in a humidifier 5000, and passes along an air circuit 4170 tothe patient 1000.

FIG. 1C shows a system including a patient 1000 wearing a patientinterface 3000, in the form of a full-face mask, receiving a supply ofair at positive pressure from an RPT device 4000. Air from the RPTdevice is humidified in a humidifier 5000, and passes along an aircircuit 4170 to the patient 1000. The patient is sleeping in a sidesleeping position.

3.2 Respiratory System and Facial Anatomy

FIG. 2A shows an overview of a human respiratory system including thenasal and oral cavities, the larynx, vocal folds, oesophagus, trachea,bronchus, lung, alveolar sacs, heart and diaphragm.

FIG. 2B shows a view of a human upper airway including the nasal cavity,nasal bone, lateral nasal cartilage, greater alar cartilage, nostril,lip superior, lip inferior, larynx, hard palate, soft palate,oropharynx, tongue, epiglottis, vocal folds, oesophagus and trachea.

FIG. 2C is a front view of a face with several features of surfaceanatomy identified including the lip superior, upper vermilion, lowervermilion, lip inferior, mouth width, endocanthion, a nasal ala,nasolabial sulcus and cheilion. Also indicated are the directionssuperior, inferior, radially inward and radially outward.

FIG. 2D is a side view of a head with several features of surfaceanatomy identified including glabella, sellion, pronasale, subnasale,lip superior, lip inferior, supramenton, nasal ridge, alar crest point,otobasion superior and otobasion inferior. Also indicated are thedirections superior & inferior, and anterior & posterior.

FIG. 2E is a further side view of a head. The approximate locations ofthe Frankfort horizontal and nasolabial angle are indicated. The coronalplane is also indicated.

FIG. 2F shows a base view of a nose with several features identifiedincluding naso-labial sulcus, lip inferior, upper Vermilion, naris,subnasale, columella, pronasale, the major axis of a naris and thesagittal plane.

FIG. 2G shows a side view of the superficial features of a nose.

FIG. 2H shows subcutaneal structures of the nose, including lateralcartilage, septum cartilage, greater alar cartilage, lesser alarcartilage, sesamoid cartilage, nasal bone, epidermis, adipose tissue,frontal process of the maxilla and fibrofatty tissue.

FIG. 2I shows a medial dissection of a nose, approximately severalmillimeters from a sagittal plane, amongst other things showing theseptum cartilage and medial crus of greater alar cartilage.

FIG. 2J shows a front view of the bones of a skull including thefrontal, nasal and zygomatic bones. Nasal concha are indicated, as arethe maxilla, and mandible.

FIG. 2K shows a lateral view of a skull with the outline of the surfaceof a head, as well as several muscles. The following bones are shown:frontal, sphenoid, nasal, zygomatic, maxilla, mandible, parietal,temporal and occipital. The mental protuberance is indicated. Thefollowing muscles are shown: digastricus, masseter, sternocleidomastoidand trapezius.

FIG. 2L shows an anterolateral view of a nose.

3.3 Patient Interface

FIG. 3A shows a patient interface in the form of a nasal mask inaccordance with one form of the present technology.

FIG. 3B shows a schematic of a cross-section through a structure at apoint. An outward normal at the point is indicated. The curvature at thepoint has a positive sign, and a relatively large magnitude whencompared to the magnitude of the curvature shown in FIG. 3C.

FIG. 3C shows a schematic of a cross-section through a structure at apoint. An outward normal at the point is indicated. The curvature at thepoint has a positive sign, and a relatively small magnitude whencompared to the magnitude of the curvature shown in FIG. 3B.

FIG. 3D shows a schematic of a cross-section through a structure at apoint. An outward normal at the point is indicated. The curvature at thepoint has a value of zero.

FIG. 3E shows a schematic of a cross-section through a structure at apoint. An outward normal at the point is indicated. The curvature at thepoint has a negative sign, and a relatively small magnitude whencompared to the magnitude of the curvature shown in FIG. 3F.

FIG. 3F shows a schematic of a cross-section through a structure at apoint. An outward normal at the point is indicated. The curvature at thepoint has a negative sign, and a relatively large magnitude whencompared to the magnitude of the curvature shown in FIG. 3E.

FIG. 3G shows a cushion for a mask that includes two pillows. Anexterior surface of the cushion is indicated. An edge of the surface isindicated. Dome and saddle regions are indicated.

FIG. 3H shows a cushion for a mask. An exterior surface of the cushionis indicated. An edge of the surface is indicated. A path on the surfacebetween points A and B is indicated. A straight line distance between Aand B is indicated. Two saddle regions and a dome region are indicated.

FIG. 3I shows the surface of a structure, with a one dimensional hole inthe surface. The illustrated plane curve forms the boundary of a onedimensional hole.

FIG. 3J shows a cross-section through the structure of FIG. 3I. Theillustrated surface bounds a two dimensional hole in the structure ofFIG. 3I.

FIG. 3K shows a perspective view of the structure of FIG. 3I, includingthe two dimensional hole and the one dimensional hole. Also shown is thesurface that bounds a two dimensional hole in the structure of FIG. 3I.

FIG. 3L shows a mask having an inflatable bladder as a cushion.

FIG. 3M shows a cross-section through the mask of FIG. 3L, and shows theinterior surface of the bladder. The interior surface bounds the twodimensional hole in the mask.

FIG. 3N shows a further cross-section through the mask of FIG. 3L. Theinterior surface is also indicated.

FIG. 3O illustrates a left-hand rule.

FIG. 3P illustrates a right-hand rule.

FIG. 3Q shows a left ear, including the left ear helix.

FIG. 3R shows a right ear, including the right ear helix.

FIG. 3S shows a right-hand helix.

FIG. 3T shows a view of a mask, including the sign of the torsion of thespace curve defined by the edge of the sealing membrane in differentregions of the mask.

3.4 RPT Device

FIG. 3U shows an RPT device in accordance with one form of the presenttechnology.

3.5 Humidifier

FIG. 3V shows an isometric view of a humidifier in accordance with oneform of the present technology.

FIG. 3W shows an isometric view of a humidifier in accordance with oneform of the present technology, showing a humidifier reservoir 5110removed from the humidifier reservoir dock 5130.

3.6 Seal-Forming Structure and Patient Interface

FIG. 4 depicts a perspective view of a seal forming structure.

FIG. 5 depicts a perspective view of a seal forming structure.

FIG. 5A depicts a perspective view of a seal forming structure where aloop includes a closed end.

FIG. 6 depicts a plan view of a seal forming structure.

FIG. 7 depicts a cross-sectional view taken along lines 7-7 of FIG. 6.

FIG. 7A depicts the same cross-sectional view as FIG. 7, but with anangle of the structure varied.

FIGS. 7B-7I depict mechanical attachments at the cross-sectional view ofFIG. 7.

FIG. 8A to 8G depict a cross-sectional views taken along correspondinglines of FIG. 6.

FIG. 9 depicts a plan view of a seal forming structure.

FIG. 10 depicts a perspective view of a seal forming structure.

FIG. 11 depicts a simplified representation of a tubular structure andflap.

FIG. 12 depicts a simplified representation of a tubular structure andflap attached to a seal forming structure.

FIG. 13 depicts a simplified representation compliance of a seal formingstructure.

FIG. 14 depicts a perspective view of a seal forming structure.

FIG. 15 depicts a cross-sectional view illustrating a rib of a sealforming structure.

FIG. 16 depicts a cross-sectional view of a rib under compression.

FIG. 17 depicts a cross-sectional view of a rib under tension.

FIGS. 18 and 19 illustrate cross-sections of a seal forming structure.

FIG. 20A depicts various regions of a seal forming structure.

FIG. 20B depicts various regions of another seal forming structure.

FIG. 20C depicts various closed paths of another seal forming structure.

FIG. 21 depicts a seal forming structure attached to a mask shell.

FIG. 22 depicts an exploded view of a seal forming structure and twoclips.

FIG. 23 depicts a view of a cushion and clip.

FIG. 23A depicts a cross-sectional view of FIG. 23 taken along line23A-23A.

FIG. 24 depicts a perspective view of a seal forming structure.

FIG. 25A depicts a front view of the seal forming structure of FIG. 24.

FIGS. 25B-25G depict various cross-sections taken along correspondinglines in FIG. 25A.

FIG. 26 depicts a rear view of the seal forming structure of FIG. 24.

FIG. 27 depicts various regions of the seal forming structure of FIG.24.

FIG. 28A is a top perspective view of a seal-forming structure for afull-face patient interface according to an example of the presenttechnology.

FIG. 28B is a front view of a seal-forming structure for a full-facepatient interface according to an example of the present technology.

FIG. 28C is a rear view of a seal-forming structure for a full-facepatient interface according to an example of the present technology.

FIG. 28D is a top view of a seal-forming structure for a full-facepatient interface according to an example of the present technology.

FIG. 28E is a bottom view of a seal-forming structure for a full-facepatient interface according to an example of the present technology.

FIG. 28F is a side view of a seal-forming structure for a full-facepatient interface according to an example of the present technology.

FIG. 28G is a bottom perspective view of a seal-forming structure for afull-face patient interface according to an example of the presenttechnology.

FIG. 28H is another top perspective view of a seal-forming structure fora full-face patient interface according to an example of the presenttechnology.

FIG. 28I is another bottom view of a seal-forming structure for afull-face patient interface according to an example of the presenttechnology.

FIG. 28J is a cross-sectional view of a seal-forming structure for afull-face patient interface taken through line 28J-28J of FIG. 28Baccording to an example of the present technology.

FIG. 28K is a cross-sectional view of a seal-forming structure for afull-face patient interface taken through line 28K-28K of FIG. 28Baccording to an example of the present technology.

FIG. 28L is a cross-sectional view of a seal-forming structure for afull-face patient interface taken through line 28L-28L of FIG. 28Baccording to an example of the present technology.

FIG. 28M is a perspective view of a seal-forming structure for afull-face patient interface shown in FIG. 28L.

FIG. 29A is a top perspective view of an assembly of a seal-formingstructure and a plenum chamber for a full-face patient interfaceaccording to an example of the present technology.

FIG. 29B is a front perspective view of an assembly of a seal-formingstructure and a plenum chamber for a full-face patient interfaceaccording to an example of the present technology.

FIG. 29C is a cross-sectional view of an assembly of a seal-formingstructure and a plenum chamber for a full-face patient interface takenthrough line 29C-29C of FIG. 29B according to an example of the presenttechnology.

FIG. 29D is a cross-sectional view of an assembly of a seal-formingstructure and a plenum chamber for a full-face patient interface takenthrough line 29D-29D of FIG. 29B according to an example of the presenttechnology.

FIG. 29E is a cross-sectional view of an assembly of a seal-formingstructure and a plenum chamber for a full-face patient interface takenthrough line 29E-29E of FIG. 29B according to an example of the presenttechnology.

FIG. 30A is a top perspective view of a full-face patient interfaceaccording to an example of the present technology.

FIG. 30B is a top perspective view of a full-face patient interfaceaccording to an example of the present technology.

FIG. 30C is a top perspective view of a full-face patient interfaceaccording to another example of the present technology.

FIG. 30D is a perspective view of the patient interface of FIG. 30C asworn by a patient.

FIG. 30E is an exploded view of the patient interface of FIG. 30C.

FIG. 30F is another exploded view of the patient interface of FIG. 30C.

FIG. 30G is another exploded view of the patient interface of FIG. 30C.

FIG. 31A is a top perspective view of a seal-forming structure for anasal patient interface according to an example of the presenttechnology.

FIG. 31B is a front view of a seal-forming structure for a nasal patientinterface according to an example of the present technology.

FIG. 31C is a rear view of a seal-forming structure for a nasal patientinterface according to an example of the present technology.

FIG. 31D is a top view of a seal-forming structure for a nasal patientinterface according to an example of the present technology.

FIG. 31E is a bottom view of a seal-forming structure for a nasalpatient interface according to an example of the present technology.

FIG. 31F is a side view of a seal-forming structure for a nasal patientinterface according to an example of the present technology.

FIG. 31G is a bottom perspective view of a seal-forming structure for anasal patient interface according to an example of the presenttechnology.

FIG. 31H is another top perspective view of a seal-forming structure fora nasal patient interface according to an example of the presenttechnology.

FIG. 31I is another bottom view of a seal-forming structure for a nasalpatient interface according to an example of the present technology.

FIG. 31J is a cross-sectional view of a seal-forming structure for anasal patient interface taken through line 31J-31J of FIG. 31B accordingto an example of the present technology.

FIG. 31K is a cross-sectional view of a seal-forming structure for anasal patient interface taken through line 31K-31K of FIG. 31B accordingto an example of the present technology.

FIG. 31L is a cross-sectional view of a seal-forming structure for anasal patient interface taken through line 31L-31L of FIG. 31B accordingto an example of the present technology.

FIG. 31M is a perspective view of a seal-forming structure for afull-face patient interface shown in FIG. 31L.

FIG. 32A is a top perspective view of an assembly of a seal-formingstructure and a plenum chamber for a nasal patient interface accordingto an example of the present technology.

FIG. 32B is a front perspective view of an assembly of a seal-formingstructure and a plenum chamber for a nasal patient interface accordingto an example of the present technology.

FIG. 32C is a cross-sectional view of an assembly of a seal-formingstructure and a plenum chamber for a nasal patient interface takenthrough line 32C-32C of FIG. 32B according to an example of the presenttechnology.

FIG. 32D is a cross-sectional view of an assembly of a seal-formingstructure and a plenum chamber for a nasal patient interface takenthrough line 32D-32D of FIG. 32B according to an example of the presenttechnology.

FIG. 32E is a cross-sectional view of an assembly of a seal-formingstructure and a plenum chamber for a nasal patient interface takenthrough line 32E-32E of FIG. 32B according to an example of the presenttechnology.

FIG. 32F is another cross-sectional view of an assembly of aseal-forming structure and a plenum chamber for a nasal patientinterface according to an example of the present technology.

FIG. 33A is a top perspective view of a nasal patient interfaceaccording to an example of the present technology.

FIG. 33B is a top perspective view of a nasal patient interfaceaccording to an example of the present technology.

FIG. 34A is a detailed side view of a seal-forming structure for afull-face patient interface according to a related technology in which atherapy pressure is applied.

FIG. 34B is a detailed side view of a seal-forming structure for afull-face patient interface according to another related technology inwhich a therapy pressure is applied.

4 DETAILED DESCRIPTION OF EXAMPLES OF THE TECHNOLOGY

Before the present technology is described in further detail, it is tobe understood that the technology is not limited to the particularexamples described herein, which may vary. It is also to be understoodthat the terminology used in this disclosure is for the purpose ofdescribing only the particular examples discussed herein, and is notintended to be limiting.

The following description is provided in relation to various exampleswhich may share one or more common characteristics and/or features. Itis to be understood that one or more features of any one example may becombinable with one or more features of another example or otherexamples. In addition, any single feature or combination of features inany of the examples may constitute a further example.

4.1 Therapy

In one form, the present technology comprises a method for treating arespiratory disorder comprising the step of applying positive pressureto the entrance of the airways of a patient 1000.

In certain examples of the present technology, a supply of air atpositive pressure is provided to the nasal passages of the patient viaone or both nares.

In certain examples of the present technology, mouth breathing islimited, restricted or prevented.

4.2 Treatment Systems

In one form, the present technology comprises an apparatus or device fortreating a respiratory disorder. The apparatus or device may comprise anRPT device 4000 for supplying pressurised air to the patient 1000 via anair circuit 4170 to a patient interface 3000.

4.3 Patient Interface

A non-invasive patient interface 3000 in accordance with one aspect ofthe present technology comprises the following functional aspects: aseal-forming structure 3100, a plenum chamber 3200, a positioning andstabilising structure 3300, a vent 3400, one form of connection port3600 for connection to air circuit 4170, and a forehead support 3700. Insome forms a functional aspect may be provided by one or more physicalcomponents. In some forms, one physical component may provide one ormore functional aspects. In use the seal-forming structure 3100 isarranged to surround an entrance to the airways of the patient so as tofacilitate the supply of air at positive pressure to the airways.

The inventors have found that if a patient interface 3000 is unable tocomfortably deliver a minimum level of positive pressure to the airwaysthat treatment may be ineffective.

The patient interface 3000 in accordance with one form of the presenttechnology is constructed and arranged to be able to provide a supply ofair at a positive pressure of at least 6 cmH20 with respect to ambient.

The patient interface 3000 in accordance with one form of the presenttechnology is constructed and arranged to be able to provide a supply ofair at a positive pressure of at least 10 cmH20 with respect to ambient.

The patient interface 3000 in accordance with one form of the presenttechnology is constructed and arranged to be able to provide a supply ofair at a positive pressure of at least 20 cmH20 with respect to ambient.

4.3.1 Seal-Forming Structure

In one form of the present technology, a seal-forming structure 3100provides a seal-forming surface, and may additionally provide acushioning function.

A seal-forming structure 3100 in accordance with the present technologymay be constructed from a soft, flexible, resilient material such assilicone.

In one form, the non-invasive patient interface 3000 comprises aseal-forming portion that forms a seal in use on an upper lip region(that is, the lip superior) of the patient's face.

In one form the non-invasive patient interface 3000 comprises aseal-forming portion that forms a seal in use on a chin-region of thepatient's face.

In certain forms of the present technology, a system is providedcomprising more than one a seal-forming structure 3100, each beingconfigured to correspond to a different size and/or shape range. Forexample, the system may comprise one form of a seal-forming structure3100 suitable for a large sized head, but not a small sized head andanother suitable for a small sized head, but not a large sized head.

In certain forms of the present technology, the seal-forming structure3100 is constructed from a biocompatible material, e.g. silicone rubber.

FIG. 4 illustrates a perspective view of a seal-forming structure 3100separated from a remainder of the patient interface 3000. The sealforming structure includes a sealing surface 3105 that is configured toform a seal around a periphery of a patient's airways. The seal may beformed around the patient's nose or the patient's nose and mouth.

The seal forming structure 3100 includes a tie, connecting portion, orloop 3110 that folds the sealing structure 3100 inwards (e.g., towardsthe patient's face in use) of an outer perimeter 3115 of the sealingstructure 3100. The outer perimeter 3115 may be generally defined as awall that supports and/or is formed continuously with the sealingsurface 3105. In this manner, the tie 3110 may form a substantiallytube-shaped structure 3120 so that the tie 3110 forms a continuousstructure (e.g., continuous circumference) with the sealing surface 3105and the outer perimeter 3115. Thus the tie 3110 may include a portion ofthe sealing surface 3105, a portion of the outer perimeter 3115 and aportion that is neither the sealing surface 3105 nor the outer perimeter3115. The portion that is neither the sealing surface 3105 nor the outerperimeter 3115 may be in the form of a flap or sheet attached orcontinuous with one end to the sealing surface and at another end withthe outer perimeter 3115. The tie 3110 may be located to be alongsidethe patient's nose, e.g., along the alar, above the nasal bone oranywhere in between. Two ties 3110 may be provided on opposite sides ofthe patient's nose. The tie 3110 may be open internally, including oneor both ends, so that the tie 3110 is internally pressurized (e.g., influid communication) with the patient's treatment pressure in use.

In one form of the present technology, the tie 3110 may extend onlypartially around the periphery of the seal forming structure 3100.

In one form, the tie 3110 and the seal forming structure 3100 do notform a closed, pressurizable structure (e.g., a bladder) such that thespace between the tie 3110 and the seal forming structure 3100 is opento the pressure in the interior of the patient interface 3000.

In one form the seal forming structure 3100 has an edge and the tie 3110holds the edge to prevent blowout at the edge.

Areas of the sealing surface 3105 other than the tie 3110 may include asealing flap 3125 that protrudes inwards towards an inner perimeter ofthe sealing structure 3100. The sealing flap 3125 may have anunconnected edge at or near a radially inner portion of the sealingsurface 3105. The sealing flap 3125 may include a portion 3125 a that isconfigured to form a seal against the sides of the nose above the nasalbones of the patient. The sealing flap 3125 may be structured to avoidsealing against the alar, e.g., by being spaced sufficiently farradially outward with respect to the alar to avoid or minimize contactwith the alar.

FIG. 5 illustrates a substantially opposite perspective view of the sealforming structure 3100 than that illustrated in FIG. 4. Thesubstantially tube-shaped structure 3120 may be more readily apparentfrom this view. FIG. 5A illustrates the tie 3110 with a closed end 3111.This figure also illustrates the seal forming structure 3100 without anunderlying cushion, and thus the seal forming structure 3100 may bereferred to as a single layer cushion.

FIG. 6 illustrates a plan view of the seal forming structure 3100 andserves as the basis for two section views illustrated in FIGS. 7 and 8.

FIG. 7 is a cross-section taken through the tie 3110. The substantiallytube-shaped structure 3120 may be more readily discerned from this view.The tie 3110 includes a relatively thick portion 3130 and a relativelythin portion 3135. The relatively thick portion 3130 may be between 1 mmand 2 mm thick, or between 1.3 mm and 1.7 mm thick, or about 1.5 mmthick. The relatively thin portion 3135 may be between 0.2 mm and 0.8 mmthick, or between 0.4 mm and 0.6 mm thick, or about 0.5 mm thick.Alternatively, the relatively thick portion 3130 may be about 2.5 to 5times as thick as the relatively thin portion 3135, or about 2.8 to 3.3times as thick as the relatively thin portion 3135, or three times asthick as the relatively thin portion 3135. The relatively thick portion3130 is illustrated to include the outer perimeter 3115 and most of thesealing surface 3105 at the tie 3110. The relatively thin portion 3135folds the sealing structure inwards and connects back to the sealforming structure 3100 at a connection point 3165 that is at or near ahinge structure 3140. The hinge structure 3140 is illustrated as alocalized, relatively thin strip or line that may provide preferentialbending or flexing at a predetermined location, which may provideflexibility for the seal forming structure 3100 to conform to thepatient's face. The relatively thick portion 3130 may provide sufficientresilience to provide an effective seal against the patients face. Therelatively thin portion 3135 may provide resistance to the sealingsurface 3105 blowing out under pressure while not causing the sealingsurface 3105 to have too much rigidity and be too stiff to form aneffective seal. Alternatively, the thicknesses of the relatively thickportion 3130 and the relatively thin portion 3135 could be the reverseof what is illustrated in FIG. 7. Or the relatively thin portion 3135could be extended to encompass the sealing surface 3105. Any combinationof thicknesses may be employed to achieve a desired combination ofsealing ability and resistance to blow out.

The connection point 3165 may be determined based upon the desired forceto be applied by, or desired resilience of, the tie 3110. For example,as illustrated in FIG. 7A, the angle 3170 formed by the relatively thinportion 3135 may be varied. As the angle 3170 is varied, the tension inthe relatively thin portion 3135 will also vary. The angle 3170 can thusbe optimized to prevent blowout and/or for patient comfort.

The angle 3170 may be predetermined in several ways. For example, if theseal forming structure 3100 is a single moulded piece, the mould used toform the seal forming structure 3100 will determine the angle 3170.Different angles can be achieved with different moulds. Alternatively,the relatively thin portion 3135 may be manufactured in an un-connectedstate so that the connection point 3165 is formed in a later assemblystep. The connection point 3165 could be a mechanical connection or anadhesive bond. If an adhesive bond is used, the connection point 3165may be continuously varied within an acceptable range of attachment.Alternatively, a mechanical attachment could be used. FIGS. 7B-7Iillustrate exemplary mechanical attachments. In FIGS. 7B-7E, theconnection point 3165 is keyed so that different angles can be achievedin a single connection point 3165. FIGS. 7B and 7C illustrate a firstconnection orientation of the keyed connection and FIGS. 7D and 7Eillustrate a second connection orientation of the keyed connection. InFIGS. 7F-7I, multiple discrete connection points 3165 are provided. Theconnection point 3165 that is selected will determine the angle 3170.FIGS. 7F and 7G illustrate a first discrete connection of the discreteconnection points and FIGS. 7H and 7I illustrate a second discreteconnection of the discrete connection points. The particular geometryillustrated in FIGS. 7B-7I is exemplary only and should not beconsidered limiting. Other keyed or discrete connection geometries maybe used.

As may be appreciated from FIG. 7, the tie 3110 may be positioned tocontact a side wall of the nose including the alar. The tie 3110 mayalso provide a continuous surface to maintain contact with the sides ofthe nose above the nasal bones of the patient.

FIG. 8A illustrates a cross-section taken through a vertical plane inFIG. 6. As may be most readily seen in FIG. 8, the tie 3110 is attachedto the wall forming the outer perimeter 3115 at an attachment portion3145. As illustrated, the attachment portion 3145 is a continuousportion of the tie 3110, which can be achieved by moulding the sealforming structure 3100 in one piece. However, the attachment portion3145 may also be achieved in any other convenient manner, e.g., byfastening a free end of the tie 3110 using some form of mechanical orchemical fastening like adhesive. The attachment portion 3145, alongwith the overall length of the tie 3110, may be chosen such thatsufficient tension is provided to the tie 3110 to counteract a blowoutof the sealing surface 3105 when pressure, e.g., therapy pressure, actson an interior surface of the tie 3110 and the seal forming structure3100 is pulled away from the patient's face and/or when insufficientheadgear tension exists.

Some or all of the sealing surface 3105 may be a region of (relatively)reduced friction. This may be achieved by providing a so-called frostedsurface. With a region of reduced friction, the sealing surface mayadhere to the patient's face less than without the region of reducedfriction. The region of reduced friction may be provided as part of thetie 3110 to allow the side(s) of the patient's nose to slide freelyalong the sealing surface 3105 and/or the tie 3110.

FIGS. 8A-8G also illustrate various cross-sections of FIG. 6 where theintersections of the cross-sections show that the seal forming structure3100 includes various saddles and domes. For simplicity, theintersections of the various cross-sections are referred to herein bytheir two-letter combination. For example, the intersection of thecross-section taken along line 8A-8A and the cross-section taken alongline 8B-8B is referred to as intersection AB.

Intersection AB is taken at a first dome region that is configured tocontact the patient's nasal ridge inferior to the patient's sellion.Intersection AC is taken at a first saddle region that is configured tocontact the patient's nasal ridge at a position inferior to intersectionAB. Intersection AD is taken at a second saddle region that isconfigured to contact the patient's lip inferior and/or supramenton.Intersection EF is taken at a second dome region that is configured tocontact the patient outside of but proximal to the patient's mouth, nearthe cheilion. Intersection EG is taken in a third saddle region that isconfigured to contact the patient's cheek adjacent the patient's nasalala. In relation to one another, the first dome region has relativelylarge curvature along both cross sections and the second dome region hasrelatively small curvature along both cross section. The first saddleregion has relatively large curvature along both cross-sections and thethird saddle region has relatively small curvature along line 8E-8E andrelatively large curvature along line 8G-8G. The second saddle regionhas curvature that is between the first saddle region and the thirdsaddle region along line 8D-8D and line 8A-8A is similar to that alongline 8G-8G.

FIG. 9 illustrates additional aspects of the present technology. Forexample, instead of the tie 3110 being continuous with the sealingsurface 3105, FIG. 9 illustrates the tie 3110 underlying the sealingsurface 3105. The tie 3110 is illustrated mostly as a dashed line. Thisconfiguration may be achieved by attaching or forming a strip or tube ofmaterial underneath the sealing surface 3105. The underlying tie 3110may be more readily apparent in FIG. 10.

FIG. 9 also illustrates a flap 3150 that may extend from the sealingsurface 3105 generally near the tie 3110 and/or the patient's nose. Sucha flap 3150 may aid in sealing and/or comfort related to the patient'snose, above the maxilla and adjacent the endocanthion. This area of thepatient's face may be difficult to seal with some known devices.Alternatively, the flap 3150 may extend from the tie 3110, which may fixthe position of the flap 3150 with respect to the tie 3110. FIG. 11illustrates a simplified representation of the tie 3110 as asubstantially tube shaped structure 3120 with the flap 3150 extendingtherefrom.

FIG. 12 illustrates a simplified representation of the substantiallytube-shaped structure 3120 illustrated in FIG. 11 attached to a sealforming structure 3100. In accordance with FIG. 12, the substantiallytube-shaped structure 3120 may be fabricated separately and fastened tothe seal forming structure 3100.

FIG. 13 illustrates how the substantially tube-shaped structure 3120provides compliance to allow the seal forming structure 3100 to adapt toa patient's face. Even while compliant, the present technology mayprevent a blowout.

Blowout may be understood to refer to the deformation of the sealforming structure 3100 that is caused, at least in part, by the pressuredifferential resulting from the application of pressure during therapysuch that the sealing surface 3105 is displaced from sealing contactwith the patient's face. For example, the patient may pull the patientinterface 3000 away from the face during therapy (i.e., while pressureis being applied) and when the patient interface 3000 is displaced fromthe patient's face by the patient, the force of the therapy pressure maycause the seal forming structure 3100 to deform. When the patientinterface 3000 is then reapplied to the patient's face by the patient,the sealing surface 3105 of the seal forming structure 3100 may bedisplaced due to deformation such that an ineffective seal is formed andpressurized gas leaks from the seal forming structure 3100. During thisrepositioning of the seal forming structure 3100, it is possible for theinternal pressurisation of the plenum chamber 3200 to be disturbed andcause a pressure gradient proximal to the sealing flap 3125. Thepressure gradient may provide a force, which may ultimately lead to blowout of the sealing flap. Displacement of the sealing flap during blowout may move the sealing flap into a position that interrupts seal byforming leak paths when the sealing structure is again repositioned ontothe face. When blowout of the seal forming structure 3100 occurs atregions proximal to the patient's eyes (e.g., when the sealing surface3105 proximal to the frontal process of the maxilla is displaced), thepressurized gas may flow towards the patient's, which may beparticularly disruptive and bothersome to the patient. Accordingly, itis advantageous to reduce blowout.

The deformation that blowout may subject the seal forming structure 3100to may be in an outward direction, e.g., away from the patient's face.Indeed, in extreme conditions under high internal pressurisation, blowout may include the seal forming structure 3100 folding backwards uponitself.

The sides of the nose, including above the nasal bones, proximal to thefrontal process of the maxilla, and lateral cartilage can be highlyvariable in profile between users. Moreover, to seal in this region theinner edge of the sealing flap 3125 may bend inwards (e.g., into theplenum chamber and orthogonal to the Frankfort horizontal) and deform tofollow the profile of the sides of the nose. As such, this area may beparticularly prone to seal interruptions following blow out. That is, ifthe sealing flap 3125 is outwardly displaced (e.g., away from thepatient's face) during blow out, it is often difficult to return thesealing flap to a sealing position due to resistance from the force ofthe pressurized gas.

However, blow out may also occur in other areas such as the cheek regionor at the upper or lower lip regions which are less prone to sealinterruption, but these regions have a generally flatter profilesubstantially along the coronal plane. During blow out, the sealing flapmay not move significantly from a position that is required to sealalong this plane and often the sealing force provided by the head gearvectors is sufficient to reposition the sealing flap to an orientationrequired to regain seal.

The posterior surface of the sealing flap at the sides of the noseregion and down the bottom corners of the sealing flaps provides alarger surface area that is more prone to displacement under internalpressurisation.

While dual wall seal forming structures 3100 may be susceptible toblowout, single wall seal forming structures 3100 such as thosedisclosed in examples of the present technology, may be particularlysusceptible to blowout. The absence of an additional undercushionstructure supporting the outer, sealing wall may be understood to allowthe outer, sealing wall to deform and deflect more easily. Moreover, theundercushion in a dual wall cushion may help to reposition the outer,sealing wall against the patient's face when the patient interface 3000is repositioned, but this assistance may be absent in a single wallcushion.

FIGS. 34A and 34B depict examples of related art patient interfaces 3000in which blowout has occurred. In FIG. 34A, the seal forming structure3100 can be seen deformed such that the sealing surface 3105 at ablowout region BR1 is displaced from the patient's nose. Additionally,the seal forming structure 3100 can be seen deformed such that thesealing surface 3105 at another blowout region BR2 is displaced from theside of the patient's nose, e.g., proximal to the frontal process of themaxilla (see FIG. 2H). Similarly, FIG. 34B depicts displacement of thesealing surface 3105 of the seal forming structure 3200 at a blowoutregion BR2 at the side of the patient's nose, e.g., proximal to thefrontal process of the maxilla.

In both examples of blowout described above, the patient interface 3000is a full-face patient interface that seals around the nose and mouth.Such patient interfaces may be particularly susceptible to blowoutbecause the relatively elongate lateral portions may be less supportedat intermediate regions and blowout may occur in these regions.Additionally, the force vectors of the positioning and stabilisingstructure 3300 may be directed generally parallel to the Frankforthorizontal plane or the sagittal plane. Thus, these force vectors maynot be directed to impart a force to the seal forming structure 3100that is generally normal to the frontal process of the maxilla in aninward direction to thereby resist the deformation of the seal formingstructure 3100 that results in blowout. In other words, the force of thetherapy pressure that causes deformation of the seal forming structure3100 may have a magnitude and direction that cannot be adequatelyopposed by the force vectors from the positioning and stabilizingstructure 3100. While the phenomenon of blowout may be especiallyrelevant for full-face patient interfaces, it should also be understoodthat nasal patient interfaces may also be susceptible to blowout basedon the same principles. Accordingly, the ties 3110 disclosed herein maybe incorporated with nasal and full-face patient interfaces to resistblowout.

Furthermore, there is also a relevant distinction in the context of thesealing surface 3105. The sealing surface 3105 may be understood tobroadly refer to the region on the seal forming structure 3100 where aseal may be intended to occur. Since the anthropometry of each patient'shead and face is different, the seal forming structure 3100 may beshaped and dimensioned to provide a comfortable fit and effective sealacross a range of patients. Therefore, it should be understood that aseal may be intended to occur across various areas of the seal formingstructure 3100 and the sealing surface 3105 may broadly refer to suchareas. Once the seal forming structure 3100 is actually applied to aparticular patient in use, a seal may be formed at a specific portion ofthe broader area in which a seal is intended to occur. That region atwhich the seal actually occurs in use may also be understood to be thesealing surface 3105. The particular meaning of the sealing surface 3105may be understood to be subject to the particular contexts in which theterm is used, as described above.

Referring back to the blowout discussion above, the occurrence ofblowout may be understood to refer to the situation in which the sealingsurface 3105 where a seal is intended to occur is displaced from thepatient's face. When such displacement occurs, at least an effectiveseal may be prevented and, more severely, no sealing contact may occurat all.

FIG. 14 illustrates another aspect of the present technology that mayprevent the seal forming structure 3100 from a blowout. Here, two ribs3155 are illustrated but any number of ribs may be provided. Forexample, a single rib or three or more ribs may be provided. Similar tothe tie 3110, each rib 3155 tends to prevent the seal forming structure3100, for example the sealing surface 3105, from blowing out. The ribsmay have the same thickness or different thicknesses. For example, oneor both ribs 3155 may be about 1 mm thick and one or both ribs 3155 maybe about 0.5 mm thick. Alternatively, the ribs may have a variablethickness. Where the ribs 3155 are attached, the sealing surface 3105may be convex and an opposite side, where the ribs 3155 attach, may beconcave. Thus the convex and concave surfaces define a thickness ofmaterial in that area. The ribs 3155 may be provided adjacent to apatient's nose.

FIG. 15 illustrates a cross section of the seal forming structure 3100taken perpendicular to a plane of a rib 3155. The rib 3155 may berelatively compliant in compression or easily crushed under sealingloads, thus allowing seal forming structure 3100 and/or the sealingsurface 3105 to adapt to the patient's face. This is illustrated in FIG.16. However, as illustrated in FIG. 17, the rib 3155 may providerelatively greater resistance in tension, which may occur when theinside of the seal forming structure 3100, e.g., a surface 3105 aopposed to the sealing surface 3105, is pressurized. In this manner, therib 3155 may tend to resist blowout of the seal forming structure 3100,e.g., the rib 3155 may become a tensile member. For example, the ribs3155 tend to keep the seal forming structure 3100 in an “as moulded”state or shape under a blow out condition.

FIGS. 18 and 19 illustrate an extended flap 3160 that may allow agreater distance D1 vs D2, to accommodate for facial variations wherethe distance between the sides of the nose and the sealing flap isvaried. The sealing surface 3105 of the extended flap 3160 may alsoprovide an effective seal against the cheeks. The arrows representpossible contact area with the patient. This type of structure isgenerally sealed using a membrane on traditional silicone masks and areprone to blow out when re-adjusting the position of the mask. The tie3110 or rib 3155 may prevent blow out from happening while stillallowing the variations in distance due to facial differences to beeffectively sealed.

FIG. 20A illustrates a view similar to FIG. 6 except that patterns areincluded on the seal forming structure 3100. The patterns designateregions 3175 of similar thickness of the seal forming structure 3100.

Region 3175A may be a relatively thin region, for example, about 0.3 mm.This region may be thin for comfort and compliance at the nasal bridge.

Region 3175B may be a very thin region, for example, about 0.2 mm. Thisreduction in thickness relative to region 3175A may reduce tensionsignificantly, which may result in minimal to no facial marking at thenasal bridge. The nasal bridge is quite bony for most patients and thusmay be prone to marking and/or discomfort.

Region 3175C may be a semi-thin region, for example, about 1 mm. Thisregion may be semi-thin to prevent pinching at the sides of the nose.

Region 3175D may be a semi-thick region, for example, about 1.5 mm. Thisregion may seal on the cheeks alongside nose. This area on the face istypically fattier then the sides of the nose or nasal bridge, whichallows for a relatively greater seal force to be applied withoutdiscomfort. The semi-thick region may also provide for more structuralrigidity than thinner regions.

Region 3175E may be a thick region, for example, about 2.0 mm. Thisthicker peripheral region may provide a more rigid outer wall to providesupport for the inner portion of the cushion. Region 3175E may act likean undercushion of prior dual layer cushion designs, e.g., the region3175E may support the portion(s) of the seal forming structure 3100 thatcontacts the patient's face. For example, region 3175E may providesupport to region 3175D and/or 3175F (discussed below). The overallcross sectional shape of the cushion may be curved to provide an air(pressure) assisted spring for seal and compliance. This configurationmay provide an advantage over the previous thick undercushions of priormasks because the disclosed configuration with this thick region maystill be able to compress to provide a level of compliance to supportforming a seal. This may increase the overall distance range in whichthe cushion can compress when compared to previous dual layer designs.

Region 3175F may be a thin membrane region, for example, about 0.3-0.5mm. The portion that seals below the lower lip may be thin, for example,about 0.3 mm, to allow for movement of the lower jaw. Such a thinmembrane region may also provide a lighter load against the patient'sgums for comfort. The portion of region 3175F adjacent region 3175D iswhere the ties 3110 are positioned. This portion of region 3175F may bethin, for example, about 0.5 mm, to allow compression of the ties 3110.The portion of region 3175F configured to contact on the sides of thepatient's mouth may be about 0.5 mm and may act like the sealingmembrane layer of the dual layer cushions, which maintain a seal withmicro variations of the facial profile and movement during sleep.

Although distinct lines are illustrated between the regions 3175, theregions may smoothly transitions in relative thickness from region toregion and thus the borders between regions are approximations. This maybe advantageous because it limits the ability to identify thick and thinregions by the naked eye, which may also be more aesthetically pleasing.However, distinct transitions may also be provided.

FIG. 20B illustrates another seal forming structure 3100 with regions ofsimilar elastomeric wall thickness of the seal forming structure 3100.

A region 3180A may be a relatively thin region, for example, about 0.3mm elastomeric wall thickness. This region may be thin for comfort andcompliance at the nasal bridge.

A region 3180B may be a very thin region, for example, about 0.2 mmelastomeric wall thickness. This reduction in thickness relative toregion 3180A may reduce tension significantly, which may result inminimal to no facial marking at the nasal bridge. The nasal bridge isquite bony for most patients and thus may be prone to marking and/ordiscomfort. In addition, the region 3180A may extend from the region3180B to a mask shell 3816 attached to the anterior side of the sealforming structure 3100.

Regions 3180A and 3180B may both straddle a sagittal plane 3185 that maybisect the seal forming structure 3100 into left and right sides. Thesagittal plane 3185 may include a line 3190 that may be tangent to theseal forming structure 3100 at only two tangent points: a first tangentpoint (superior tangent point) 3195 and a second tangent point (inferiortangent point) 3196. Either region 3180A or region 3180B may include thefirst tangent point 3195. If not including the first tangent point 3195,the region 3180A or 3180B may be within the vicinity of the firsttangent point 3195.

A portion of the region 3180B may also be configured to seal against thesides of the nose over the nasal bones and/or lateral cartilage. Theportion of the region 3180B may be configured to, in use, contact thesides of the nose and/or the lateral cartilage prior to the seal formingstructure contacting other parts of the face to form a seal. The portionof the region 3180B may also be very thin to prevent excessive force andpinching at the sides of the nose to avoid occlusion of the airways.

In addition, a central opening 3197 defined by a posterior side of theseal forming structure 3100 may be narrower in the region 3180B so thatthe seal forming structure 3100 is more compliant in the directiontoward and away from the sides of the patient's nose (i.e., along aplane that is orthogonal to the sagittal plane 3185).

A region 3180C may be a semi-thin region, for example, about 0.85 mm.This region may be semi-thin to prevent pinching at the sides of thenose. In addition, the region 3180C may border on both the region 3180Aand the region 3180B.

A region 3180D may be a transition region in which the elastomeric wallthickness varies. In particular, the elastomeric wall thickness of theseal forming structure 3100 in the region 3180D may decrease thedirection toward the central opening 3197. For example, the elastomericwall thickness may decrease from about 2.0 mm to 1.3 mm. The change inelastomeric wall thickness may be gradual or abrupt. In addition, theregion 3180D may border on the regions 3180 A and 3180C but not theregion 3180B.

The tie 3110 may extend from the region 3180D and/or the region 3180C.

A region 3180E may be a thick region, for example, about 2.0 mmelastomeric wall thickness. This thicker peripheral region may provide amore rigid outer wall to provide support for the inner portion of thecushion. The region 3180E may act like an undercushion of prior duallayer cushion designs, e.g., the region 3180E may support the portion(s)of the seal forming structure 3100 that contacts the patient's face. Inaddition, the region 3180E may border on the regions 3180D and 3180A butnot the regions 3180B and 3180C.

The overall cross sectional shape of the cushion may be curved toprovide an air (pressure) assisted spring for seal and compliance. Thisconfiguration may provide an advantage over the previous thickundercushions of prior masks because the disclosed configuration withthis thick region may still be able to compress to provide a level ofcompliance to support forming a seal. This may increase the overalldistance range in which the cushion can compress when compared toprevious dual layer designs.

The region 3180F may be a semi-thick region, for example, about 1.3 mmelastomeric wall thickness. This region may seal on the cheeks alongsidethe mouth. This area on the face is typically fattier then the sides ofthe nose or nasal bridge, which allows for a relatively greater sealforce to be applied without discomfort. The semi-thick region may alsoprovide for more structural rigidity than thinner regions. The region3180 f may border on the region 3180D and the region 3180C but not theregions 3180A, 3180B or 3180E.

The region 3180G may be a thin membrane region, for example, about 0.3mm elastomeric wall thickness. The portion that seals below the lowerlip may be thin to allow for movement of the lower jaw. Such a thinmembrane region may also provide a lighter load against the patient'sgums for comfort. The region 3180G may act like the sealing membranelayer of the dual layer cushions, which maintain a seal with microvariations of the facial profile and movement during sleep. In addition,the region 3180G may extend from the central opening 3197 to the maskshell 3816 attached to the anterior side of the seal forming structure3100. The region 3180G may also border on the region 3180D, the region3180E and the region 3180F but not the regions 3180A, 3180B or 3180C.

A region 3180H may be a flap region extending from the tie 3110. Theelastomeric wall thickness in the region 3180H may be 0.5 mm. Inaddition, the region 3180H may be configured to move independently ofthe tie 3110. The region 3180H may border the region 3180B, the region3180C and the region 3180F but not the regions 3180A, 3180D, 3180E or3180G.

Although distinct lines are illustrated between the regions 3175, theregions may smoothly transitions in relative thickness from region toregion and thus the borders between regions are approximations. This maybe advantageous because it limits the ability to identify thick and thinregions by the naked eye, which may also be more aesthetically pleasing.However, distinct transitions may also be provided.

In view of FIGS. 8A-8G, it should be understood that the regions 3180Athrough 3180H have various curvatures. For example, at least a portionof the region 3180A may be a dome-shaped region, while the region 3180Bmay have a saddle shape. In addition, various portions of the regions3180C, 3180D, 3180E, 3180F and 3180H may be saddle-shaped, dome-shapedor cylinder-shaped. In addition, the region 3180G may be saddle-shaped.

FIG. 20C illustrates the sealing surface 3105. A region 3198A in theupper portion of the sealing surface 3105 may have relatively reducedfriction. This may be achieved by providing a so-called frosted surface.With a region of reduced friction, the sealing surface may adhere to thepatient's face less than without the region of reduced friction. Theregion of reduced friction may be provided as part of the tie 3110 toallow the side(s) of the patient's nose to slide freely along thesealing surface 3105 and/or the tie 3110. The region 3198B in theremaining portion of the sealing surface 3105. The tackier surface mayprevent or reduce the likelihood of leakage due to movement of thepatient's chin.

FIG. 20C also shows a plurality of closed paths 3199A on the continuoussurface around the central opening 3197. The closed paths 3199A may beconcentric to the central opening 3197. For the purposes of thisdisclosure, paths that are concentric to the central opening 3197 maysubstantially follow the shape of the central opening 3197 and may be aparticular distance from the central opening 3197 throughout the pathwhen viewed head-on (i.e., the point of view shown in FIG. 20C). FIG.20C also shows one of the plurality of open paths 3199B extending fromthe central opening 3197 to the mask shell 3816.

International Patent Application Publication No. WO 2006/074513discloses cushions, which are incorporated by reference in theirentirety. In such cushions, a thicker undercushion and thinner membranelayer are disclosed. The thinner membrane provides a light seal on theface under pressure (i.e. inflates), while the undercushion providesstructural support to support sealing. The curved cross section providesa pressure assisted spring to support seal under headgear tension.

In contrast, a seal forming structure 3100 with the one or more of theregions 3175 described above may have only a single layer, which maycombine functions of the membrane and undercushion of WO 2006/074513.The maximum thickness of the cross section of the regions 3175 (e.g.,region 3175E) may be thinner than the maximum thickness of theundercushion of WO 2006/074513. However, combining the undercushion andmembrane into a single layer allows for sufficient structural rigidityto hold the shape of the cushion and support sealing action. Moreover,the reduced maximum thickness allows the single layer of the sealforming structure 3100 to be compressible by a greater distance comparedto the previous dual layer design, thereby allowing for added compliancebefore bottoming out.

International Patent Application Publication WO 2014/117227 discloses asystem with a mask where a foam cushion is supported by a flexible clipthat is attached to a second, more rigid clip, each of which is herebyincorporated by reference in its entirety. FIG. 21 discloses a similarsystem but with two ribs 3155 having been incorporated, where the ribsconfigured to be on opposed sides of a patient's nose. Only one rib isvisible in FIG. 21. These ribs act as ties that prevent the flexibleclip and attached foam seal from blowing out. Although ribs 3155 areillustrated, ties 3110 could be substituted for the ribs 3155.

Thus, in another example of the present technology, the seal formingstructure 3100 may comprise a cushion 3810, which may be made with foam.The cushion defines a single area that peripherally covers the patient'snose, in the case of a nasal mask, and the nose and mouth, in the caseof a full face mask. The foam cushion may, for example, be made from anysuitable material such as one or more of the following examplematerials: Polyethylene, Polyurethane, Ethylene vinyl acetate (EVA). Insome cases, the foam cushion may be a semi-open closed cell foam, suchas one made of polyurethane. The cushion of semi-open cell foam may havea limited permeability such as in the ranges described in more detail inInternational Patent Application Publication WO 2014/117227, where thepermeability disclosed therein is incorporated herein by reference.

The cushion 3810 may have a substantially triangular or pear-like shapewith a sealing face that follows the contours of a user's face. The foamcushion is designed to be attached to a first support (e.g., flexible)clip 3812 that is itself attached to a second, more rigid, clip 3814 (asshown in FIG. 22) or directly to the mask shell 3816. In one embodiment,the first support clip 3812 can be a flexible clip that is more rigidthan the foam cushion, but softer or more flexible than the second clip3814. It is the combination of the foam and a flexible clip that definethe physical properties of the overall sealing interface. The flexibleclip allows the interface to accommodate major variations, and tosuccessfully conform to the contours of the patient's face. Thecompliant nature of the foam cushion provides micro-adjustment and formsa comfort interface layer that interacts with the patient's skin.

The first support clip 3812 may be prone to blowing out due to itsflexible and compliant nature. FIG. 21 illustrates another aspect of thepresent technology that may prevent the first support clip 3812 and theattached cushion 3810 from a blowout. Here, the configurationillustrated includes two ribs 3155 (only one being visible due to thesymmetric nature and orientation of the figure) but any number of ribsmay be provided. For example, a single rib or three or more ribs may beprovided. Similar to the tie 3110, each rib 3155 tends to prevent thefirst support clip 3812 and the attached cushion 3810 from blowing outby functioning as a tensile member. The ribs may have the same thicknessor different thicknesses. For example, one or both ribs 3155 may beabout 1 mm thick and one or both ribs 3155 may be about 0.5 mm thick.Alternatively, the ribs may have a variable thickness. The ribs 3155 maybe provided adjacent to a patient's nose.

FIG. 21 illustrates a side view of a cushion assembly 3800 comprisingthe seal forming structure 3100 including a mask shell 3816, apermanently attached flexible first supporting clip 3812 and a foamcushion 3810. As illustrated, the flexible first supporting clip may befixed to the mask shell 3816 via a pair of ribs 3155 that act as ties toprevent blow out. The ribs 3155 may be relatively compliant incompression or easily crushed under sealing loads, thus allowing theseal forming structure 3100 to adapt to the patient's face. The tensionprovided by the ribs 3155 may be adjusted by altering any one or more ofits material composition, geometry or position of the ribs 3155.

FIG. 23 illustrates the foam cushion 3810 and flexible first supportingclip 3812 where the patient contacting surface is visible. FIG. 23A is across-section taken along a vertical plane of symmetry through FIG. 23and illustrates the foam cushion, flexible first supporting clip 3812and rib 3155.

In another example of the present technology, the seal forming structure3100 may comprise a pair of ties 3110 to prevent blow out of the firstsupport clip 3812. Each tie 3110 is formed by an inward fold of theflexible supporting clip 3812 of an outer perimeter to form a connectionpoint 3165. In this manner, the tie 3110 may form a substantiallytube-shaped structure 3120. The tie forms a tie to resist blowing outfrom internal pressurisation of the plenum chamber. The tension providedby the ribs 3155 may be adjusted by altering any one or more of itsmaterial composition, geometry or position of the connection point 3165of position the tie 3110.

FIGS. 24-27 illustrate a seal forming structure 6000 similar to the sealforming structure 3100 except as noted herein. Like reference numbersare similar to those described above regarding the seal formingstructure 3100 and thus further description not repeated here. The sealforming structure 6000 illustrated in FIGS. 24-27 may have featuresgenerally suitable for use with a nasal mask.

FIGS. 25B-25G also illustrate various cross-sections of FIG. 25A wherethe intersections of the cross-sections show that the seal formingstructure 6000 includes various saddles and domes. For simplicity, theintersections of the various cross-sections are referred to herein bytheir two-letter combination. For example, the intersection of thecross-section taken along line 25B-25B and the cross-section taken alongline 25C-25C is referred to as intersection BC.

Intersection BC is taken at a first saddle region that is configured tocontact the patient's nasal ridge inferior to the patient's sellion.Along line 25B-25B, the curvature is relatively small and along line25C-25C the curvature is relatively large. The curvature along line25B-25B is sufficiently large that the first saddle region isapproaching a cylindrical region. The first saddle region may be acylindrical region if so desired. Intersection BD is taken at a secondsaddle region that is configured to contact the patient's lip superior.Along line 25B-25B the curvature is relatively small compared to alongline 25D-25D. Intersection CF is taken at a first dome region that isconfigured to contact the patient's nose adjacent the nasal ridge. Alongline 25F-25F the and along line 25C-25C the curvatures are relativelysimilar. Intersection FG is taken at a third saddle region formed by thetie 3110 that is configured to contact alongside the patient's nose. Thecurvature along line 25F-25F is relatively small and is approaching zerocurvature. The curvature along line 25G-25G is relatively largecomparted to line 25F-25F. Thus the third saddle region is approaching acylindrical region and thus may be a cylindrical region if preferred.Intersection EF is taken at a second dome region that is configured tocontact the patient alongside the patient's nasal alar. The curvaturesalong lines 22E-22D and 22F-22F are relatively similar.

FIG. 27 illustrates a view of the seal forming structure 6000 exceptthat patterns are included on the seal forming structure 6000. Thepatterns designate regions 6005 of similar properties and/or thicknessof the seal forming structure 6000.

Region 6005A, referred to herein as a nasal region, may have a thicknessof about 0.5 mm, which may prevent crinkling and/or creasing of the sealforming structure 6000 in this region.

Region 6005B, referred to herein as a base region, may have a thicknessbetween about 2.9 mm to 3.45 mm. For example, the thickness may be 2.9mm at 6005B2, 3.0 mm at 6005B1 and 6005B3 and 3.45 mm at 6005B4. Region6005B may provide a support or base for the sealing flap 3125 and mayprovide and maintain the overall shape of the seal forming structure6000.

Region 6005C, referred to herein as an under-cushion zone, may have athickness ranging from 0.95 mm to 2.1 mm. As illustrated, this regionmay be the predominant region of the cushion. For example, region 6005Cmay be approximately 50% of the cushion. Thickness of the upper portionof the region 6005C1 may be between 0.95 mm and 1.6 mm whereas thicknessof the lower portion of the region 6005C2 may be between 1.25 mm and 2.1mm. The thickness may be continuously varying between these values toprovide a smooth appearance.

Region 6005D, referred to herein as a membrane region, may formapproximately one third of the seal forming structure 6000 and mayinclude the ties 3110. The thickness may be about 0.35 mm. This regionmay be relatively thin so that it may function as an energized (e.g.,pressure activated) seal against the patient's face. The side sections6005D1 may be substantially parallel to the patient's face, which mayreduce the likelihood of creasing and thus causing a leak. Such creasesmay be more likely to occur during dynamic situations, e.g., when theseal is under movement.

Region 6005F, referred to herein as a spring zone, may have a thicknessranging from 1.1 mm to 1.8 mm. This zone may function as a spring andallow for compression on the lip superior to reduce pressure thereon.This region may get progressively stiffer from the center of the lipsuperior to the corners of the nose (e.g., the alar crest point) whereregion 6005F is stiffest.

Region 6005G, referred to herein as a nose dip region, may be relativelydeeper to better accommodate patients that have a relatively high nasalbridge and/or provide a more comfortable seal. This region may have athickness similar to that of region 6005D (e.g., about 0.35 mm) and thusmay be a sub-region of region 6005D.

The expressions “soft” and “flexible”, as well as their derivatives,when used in this specification to describe the first support clip 3812,are intended to have the meaning of the expression “resilient” asspecifically defined in section “Terms used in relation to patientinterface”. This is to say, the flexible supporting clip is able todeform substantially elastically, and to quickly release substantiallyall of the energy upon unloading.

The seal forming structure 3100 may have advantages in one or more formsof the present technology. For example, the human facial structure mayinclude variations from person to person that provide challenges whendesigning a seal for use with many facial variations. The variations mayinclude different shapes of the facial structure (e.g., differentlyshaped noses and/or differently curved cheeks) and/or different tissuecontent (e.g., more or less fatty tissue). These variations may resultin a prior seal forming structure that works very well for one personbut poorly for another. Also, perceived comfort may vary from person toperson independent of facial structure. With the seal forming structure3100 described herein, a higher percentage of users may use the sealforming structure 3100 effectively (e.g., a higher percentage of usersmay have the seal forming structure 3100 form an effective seal and/or ahigher percentage of users may perceive the seal forming structure 3100to be comfortable) than compared to prior seal forming structures.

FIGS. 28A to 28M depict an exemplary full-face seal forming structure3100 that includes the ties 3110. As can be seen in FIG. 28K, forexample, the ties 3110 may extend between a first interior surfaceregion 3180 and a second interior surface region 3185. The firstinterior surface region 3180 may be understood to be opposite thesealing surface 3105 of the seal forming structure. The second interiorsurface region 3185 may be understood to be located elsewhere. In theexample depicted in FIG. 28k , the second interior surface region 3185is located on the interior of the seal forming structure 3100. In otherexamples, the second interior surface region 3185 may be located on theinterior of the plenum chamber 3200 such that the tie 3110 extendsbetween the seal forming structure 3100 and the plenum chamber 3200. Thelocation of the second interior surface region 3185 may be selectedbased on the desired directional component of the tension vector of thetie 3100 that resists the blowout force.

FIGS. 28L and 28M show detailed cross-sectional views and, inparticular, the connection point 3165 where the tie 3110 extends fromthe second interior surface region 3165. The connection point 3165 inthis example may be curved to reduce stress concentration in thisregion, thereby reducing the tendency for the tie 3110 to tear.Furthermore, the tie 3110 may extend from the second interior surfaceregion 3185 at a distance from a bonding region 3190 where the sealforming structure 3100 is bonded to the plenum chamber 3200 duringproduction. This may prevent damage to the tie 3110 when the sealforming structure 3100 is bonded to the plenum chamber 3200. FIGS. 29Cto 29E also show how the tie 3110 extends from the second interiorsurface region 3185 at a distance from the bonding region 3190 and theplenum chamber 3200.

The cross-sectional views of FIGS. 28J to 28L also show where the tie3110 may extend from the first interior surface region 3180. As can beseen in these examples, the tie 3110 extends from the first interiorsurface region 3110 near, but not at the edge of the sealing flap 3125.However, in alternative examples the tie 3110 may extend from the firstinterior surface region 3180 closer to or at the edge of the sealingflap 3125.

FIGS. 30A and 30B depict examples of a full-face patient interface 3000including a seal forming structure 3100 with features of the presenttechnology, but without a positioning and stabilizing structure 3300depicted.

FIGS. 31A to 31M depict another example of the present technology whichis a nasal seal forming structure 3100. As can be seen in FIG. 31K, forexample, the tie 3110 extends contiguously from the sealing flap 3125.Accordingly, there may not be a defined edge in this region. Moreover,it should also be understood that at least a portion of the tie 3110 insuch an arrangement may form part of the sealing surface 3105 in use,depending on the patient's facial anthropometry.

FIGS. 32C to 32E show that in the nasal patient interface 3000 examplethat the tie 3110 may extend from the second interior surface region3185 at a further distance from the bonding region 3190 as compared tothe full-face patient interface 3000.

4.3.2 Plenum Chamber

The plenum chamber 3200 has a perimeter that is shaped to becomplementary to the surface contour of the face of an average person inthe region where a seal will form in use. In use, a marginal edge of theplenum chamber 3200 is positioned in close proximity to an adjacentsurface of the face. Actual contact with the face is provided by theseal-forming structure 3100. The seal-forming structure 3100 may extendin use about the entire perimeter of the plenum chamber 3200.

In certain forms of the present technology, the plenum chamber 3200 isconstructed from a transparent material, e.g. a transparentpolycarbonate. The use of a transparent material can reduce theobtrusiveness of the patient interface, and help improve compliance withtherapy. The use of a transparent material can aid a clinician toobserve how the patient interface is located and functioning.

In certain forms of the present technology, the plenum chamber 3200 isconstructed from a translucent material. The use of a translucentmaterial can reduce the obtrusiveness of the patient interface, and helpimprove compliance with therapy.

4.3.3 Positioning and Stabilising Structure

The seal-forming structure 3100 of the patient interface 3000 of thepresent technology may be held in sealing position in use by thepositioning and stabilising structure 3300.

In one form the positioning and stabilising structure 3300 provides aretention force at least sufficient to overcome the effect of thepositive pressure in the plenum chamber 3200 to lift off the face.

In one form the positioning and stabilising structure 3300 provides aretention force to overcome the effect of the gravitational force on thepatient interface 3000.

In one form the positioning and stabilising structure 3300 provides aretention force as a safety margin to overcome the potential effect ofdisrupting forces on the patient interface 3000, such as from tube drag,or accidental interference with the patient interface.

In one form of the present technology, a positioning and stabilisingstructure 3300 is provided that is configured in a manner consistentwith being worn by a patient while sleeping. In one example thepositioning and stabilising structure 3300 has a low profile, orcross-sectional thickness, to reduce the perceived or actual bulk of theapparatus. In one example, the positioning and stabilising structure3300 comprises at least one strap having a rectangular cross-section. Inone example the positioning and stabilising structure 3300 comprises atleast one flat strap.

In one form of the present technology, a positioning and stabilisingstructure 3300 is provided that is configured so as not to be too largeand bulky to prevent the patient from lying in a supine sleepingposition with a back region of the patient's head on a pillow.

In one form of the present technology, a positioning and stabilisingstructure 3300 is provided that is configured so as not to be too largeand bulky to prevent the patient from lying in a side sleeping positionwith a side region of the patient's head on a pillow.

In one form of the present technology, a positioning and stabilisingstructure 3300 comprises a strap constructed from a laminate of a fabricpatient-contacting layer, a foam inner layer and a fabric outer layer.In one form, the foam is porous to allow moisture, (e.g., sweat), topass through the strap. In one form, the fabric outer layer comprisestie material to engage with a hook material portion.

In certain forms of the present technology, a positioning andstabilising structure 3300 comprises a strap that is extensible, e.g.resiliently extensible. For example the strap may be configured in useto be in tension, and to direct a force to draw a cushion into sealingcontact with a portion of a patient's face. In an example the strap maybe configured as a tie.

In certain forms of the present technology, a positioning andstabilising structure 3300 comprises a strap that is bendable and e.g.non-rigid. An advantage of this aspect is that the strap is morecomfortable for a patient to lie upon while the patient is sleeping.

In certain forms of the present technology, a positioning andstabilising structure 3300 comprises a strap constructed to bebreathable to allow moisture vapour to be transmitted through the strap,

In certain forms of the present technology, a system is providedcomprising more than one positioning and stabilizing structure 3300,each being configured to provide a retaining force to correspond to adifferent size and/or shape range. For example, the system may compriseone form of positioning and stabilizing structure 3300 suitable for alarge sized head, but not a small sized head, and another. suitable fora small sized head, but not a large sized head.

4.3.4 Vent

In one form, the patient interface 3000 includes a vent 3400 constructedand arranged to allow for the washout of exhaled gases, e.g. carbondioxide.

One form of the vent 3400 in accordance with the present technologycomprises a plurality of holes, for example, about 20 to about 80 holes,or about 40 to about 60 holes, or about 45 to about 55 holes.

The vent 3400 may be located in the plenum chamber 3200. Alternatively,the vent 3400 is located in a decoupling structure, e.g., a swivel.

4.3.5 Decoupling Structure(s)

In one form the patient interface 3000 includes at least one decouplingstructure, for example, a swivel or a ball and socket.

4.3.6 Connection Port

Connection port 3600 allows for connection to the air circuit 4170.

4.3.7 Forehead Support

In one form, the patient interface 3000 includes a forehead support3700.

4.3.8 Anti-Asphyxia Valve

In one form, the patient interface 3000 includes an anti-asphyxia valve.

4.3.9 Ports

In one form of the present technology, a patient interface 3000 includesone or more ports that allow access to the volume within the plenumchamber 3200. In one form this allows a clinician to supply supplementaloxygen. In one form, this allows for the direct measurement of aproperty of gases within the plenum chamber 3200, such as the pressure.

4.4 RPT DEVICE

An RPT device 4000 in accordance with one aspect of the presenttechnology comprises mechanical, pneumatic, and/or electrical componentsand is configured to execute one or more algorithms 4300. The RPT device4000 may be configured to generate a flow of air for delivery to apatient's airways, such as to treat one or more of the respiratoryconditions described elsewhere in the present document.

The RPT device may have an external housing 4010, formed in two parts,an upper portion 4012 and a lower portion 4014. Furthermore, theexternal housing 4010 may include one or more panel(s) 4015. The RPTdevice 4000 comprises a chassis 4016 that supports one or more internalcomponents of the RPT device 4000. The RPT device 4000 may include ahandle 4018.

The pneumatic path of the RPT device 4000 may comprise one or more airpath items, e.g., an inlet air filter 4112, an inlet muffler 4122, apressure generator 4140 capable of supplying air at positive pressure(e.g., a blower 4142), an outlet muffler 4124 and one or moretransducers 4270, such as pressure sensors 4272 and flow rate sensors4274.

One or more of the air path items may be located within a removableunitary structure which will be referred to as a pneumatic block 4020.The pneumatic block 4020 may be located within the external housing4010. In one form a pneumatic block 4020 is supported by, or formed aspart of the chassis 4016.

The RPT device 4000 may have an electrical power supply 4210, one ormore input devices 4220, a central controller 4230, a therapy devicecontroller 4240, a pressure generator 4140, one or more protectioncircuits 4250, memory 4260, transducers 4270, data communicationinterface 4280 and one or more output devices 4290. Electricalcomponents 4200 may be mounted on a single Printed Circuit BoardAssembly (PCBA) 4202. In an alternative form, the RPT device 4000 mayinclude more than one PCBA 4202.

4.4.1 RPT Device Mechanical & Pneumatic Components

An RPT device may comprise one or more of the following components in anintegral unit. In an alternative form, one or more of the followingcomponents may be located as respective separate units.

4.4.1.1 Air Filter(s)

An RPT device in accordance with one form of the present technology mayinclude an air filter 4110, or a plurality of air filters 4110.

In one form, an inlet air filter 4112 is located at the beginning of thepneumatic path upstream of a pressure generator 4140.

In one form, an outlet air filter 4114, for example an antibacterialfilter, is located between an outlet of the pneumatic block 4020 and apatient interface 3000.

4.4.1.2 Muffler(s)

An RPT device in accordance with one form of the present technology mayinclude a muffler 4120, or a plurality of mufflers 4120.

In one form of the present technology, an inlet muffler 4122 is locatedin the pneumatic path upstream of a pressure generator 4140.

In one form of the present technology, an outlet muffler 4124 is locatedin the pneumatic path between the pressure generator 4140 and a patientinterface 3000.

4.4.1.3 Pressure Generator

In one form of the present technology, a pressure generator 4140 forproducing a flow, or a supply, of air at positive pressure is acontrollable blower 4142. For example the blower 4142 may include abrushless DC motor 4144 with one or more impellers housed in a volute.The blower may be capable of delivering a supply of air, for example ata rate of up to about 120 litres/minute, at a positive pressure in arange from about 4 cmH₂O to about 20 cmH₂O, or in other forms up toabout 30 cmH₂O. The blower may be as described in any one of thefollowing patents or patent applications the contents of which areincorporated herein by reference in their entirety: U.S. Pat. Nos.7,866,944; 8,638,014; 8,636,479; and PCT Patent Application PublicationNo. WO 2013/020167.

The pressure generator 4140 is under the control of the therapy devicecontroller 4240.

In other forms, a pressure generator 4140 may be a piston-driven pump, apressure regulator connected to a high pressure source (e.g. compressedair reservoir), or a bellows.

4.4.1.4 Transducer(s)

Transducers may be internal of the RPT device, or external of the RPTdevice. External transducers may be located for example on or form partof the air circuit, e.g., the patient interface. External transducersmay be in the form of non-contact sensors such as a Doppler radarmovement sensor that transmit or transfer data to the RPT device.

4.4.2 RPT Device Electrical Components

4.4.2.1 Power Supply

A power supply 4210 may be located internal or external of the externalhousing 4010 of the RPT device 4000.

In one form of the present technology, power supply 4210 provideselectrical power to the RPT device 4000 only. In another form of thepresent technology, power supply 4210 provides electrical power to bothRPT device 4000 and humidifier 5000.

4.4.2.2 Input Devices

In one form of the present technology, an RPT device 4000 includes oneor more input devices 4220 in the form of buttons, switches or dials toallow a person to interact with the device. The buttons, switches ordials may be physical devices, or software devices accessible via atouch screen. The buttons, switches or dials may, in one form, bephysically connected to the external housing 4010, or may, in anotherform, be in wireless communication with a receiver that is in electricalconnection to a central controller.

4.4.2.3 Output Devices Including Optional Display, Alarms

An output device in accordance with the present technology may take theform of one or more of a visual, audio and haptic unit. A visual displaymay be a Liquid Crystal Display (LCD) or Light Emitting Diode (LED)display.

4.5 AIR CIRCUIT

An air circuit 4170 in accordance with an aspect of the presenttechnology is a conduit or a tube constructed and arranged to allow, inuse, a flow of air to travel between two components such as RPT device4000 and the patient interface 3000.

In particular, the air circuit 4170 may be in fluid connection with theoutlet of the pneumatic block 4020 and the patient interface. The aircircuit may be referred to as an air delivery tube. In some cases theremay be separate limbs of the circuit for inhalation and exhalation. Inother cases a single limb is used.

In some forms, the air circuit 4170 may comprise one or more heatingelements configured to heat air in the air circuit, for example tomaintain or raise the temperature of the air. The heating element may bein a form of a heated wire circuit, and may comprise one or moretransducers, such as temperature sensors. In one form, the heated wirecircuit may be helically wound around the axis of the air circuit 4170.The heating element may be in communication with a controller such as acentral controller. One example of an air circuit 4170 comprising aheated wire circuit is described in U.S. Pat. No. 8,733,349, which isincorporated herewithin in its entirety by reference.

4.6 HUMIDIFIER

4.6.1 Humidifier Overview

In one form of the present technology there is provided a humidifier5000 (e.g. as shown in FIGS. 3V and 3W) to change the absolute humidityof air or gas for delivery to a patient relative to ambient air.Typically, the humidifier 5000 is used to increase the absolute humidityand increase the temperature of the flow of air (relative to ambientair) before delivery to the patient's airways.

The humidifier 5000 may comprise a humidifier reservoir 5110, ahumidifier inlet 5002 to receive a flow of air, and a humidifier outlet5004 to deliver a humidified flow of air. In some forms, as shown inFIG. 3V and FIG. 3W, an inlet and an outlet of the humidifier reservoir5110 may be the humidifier inlet 5002 and the humidifier outlet 5004respectively. The humidifier 5000 may further comprise a humidifier base5006, which may be adapted to receive the humidifier reservoir 5110 andcomprise a heating element 5240.

4.6.2 Humidifier Components

4.6.2.1 Water Reservoir

According to one arrangement, the humidifier 5000 may comprise a waterreservoir 5110 configured to hold, or retain, a volume of liquid (e.g.water) to be evaporated for humidification of the flow of air. The waterreservoir 5110 may be configured to hold a predetermined maximum volumeof water in order to provide adequate humidification for at least theduration of a respiratory therapy session, such as one evening of sleep.Typically, the reservoir 5110 is configured to hold several hundredmillilitres of water, e.g. 300 millilitres (ml), 325 ml, 350 ml or 400ml. In other forms, the humidifier 5000 may be configured to receive asupply of water from an external water source such as a building's watersupply system.

According to one aspect, the water reservoir 5110 is configured to addhumidity to a flow of air from the RPT device 4000 as the flow of airtravels therethrough. In one form, the water reservoir 5110 may beconfigured to encourage the flow of air to travel in a tortuous paththrough the reservoir 5110 while in contact with the volume of watertherein.

According to one form, the reservoir 5110 may be removable from thehumidifier 5000, for example in a lateral direction as shown in FIG. 3Vand FIG. 3W.

The reservoir 5110 may also be configured to discourage egress of liquidtherefrom, such as when the reservoir 5110 is displaced and/or rotatedfrom its normal, working orientation, such as through any aperturesand/or in between its sub-components. As the flow of air to behumidified by the humidifier 5000 is typically pressurised, thereservoir 5110 may also be configured to prevent losses in pneumaticpressure through leak and/or flow impedance.

4.6.2.2 Conductive Portion

According to one arrangement, the reservoir 5110 comprises a conductiveportion 5120 configured to allow efficient transfer of heat from theheating element 5240 to the volume of liquid in the reservoir 5110. Inone form, the conductive portion 5120 may be arranged as a plate,although other shapes may also be suitable. All or a part of theconductive portion 5120 may be made of a thermally conductive materialsuch as aluminium (e.g. approximately 2 mm thick, such as 1 mm, 1.5 mm,2.5 mm or 3 mm), another heat conducting metal or some plastics. In somecases, suitable heat conductivity may be achieved with less conductivematerials of suitable geometry.

4.6.2.3 Humidifier Reservoir Dock

In one form, the humidifier 5000 may comprise a humidifier reservoirdock 5130 (as shown in FIG. 3V) configured to receive the humidifierreservoir 5110. In some arrangements, the humidifier reservoir dock 5130may comprise a locking feature such as a locking lever 5135 configuredto retain the reservoir 5110 in the humidifier reservoir dock 5130.

4.6.2.4 Water Level Indicator

The humidifier reservoir 5110 may comprise a water level indicator 5150as shown in FIG. 3V-3W. In some forms, the water level indicator 5150may provide one or more indications to a user such as the patient 1000or a care giver regarding a quantity of the volume of water in thehumidifier reservoir 5110. The one or more indications provided by thewater level indicator 5150 may include an indication of a maximum,predetermined volume of water, any portions thereof, such as 25%, 50% or75% or volumes such as 200 ml, 300 ml or 400 ml.

4.6.2.5 Heating Element

A heating element 5240 may be provided to the humidifier 5000 in somecases to provide a heat input to one or more of the volume of water inthe humidifier reservoir 5110 and/or to the flow of air. The heatingelement 5240 may comprise a heat generating component such as anelectrically resistive heating track. One suitable example of a heatingelement 5240 is a layered heating element such as one described in thePCT Patent Application Publication No. WO 2012/171072, which isincorporated herewith by reference in its entirety.

In some forms, the heating element 5240 may be provided in thehumidifier base 5006 where heat may be provided to the humidifierreservoir 5110 primarily by conduction as shown in FIG. 5B.

4.7 GLOSSARY

For the purposes of the present technology disclosure, in certain formsof the present technology, one or more of the following definitions mayapply. In other forms of the present technology, alternative definitionsmay apply.

4.7.1 General

Air: In certain forms of the present technology, air may be taken tomean atmospheric air, and in other forms of the present technology airmay be taken to mean some other combination of breathable gases, e.g.atmospheric air enriched with oxygen.

Ambient: In certain forms of the present technology, the term ambientwill be taken to mean (i) external of the treatment system or patient,and (ii) immediately surrounding the treatment system or patient.

For example, ambient humidity with respect to a humidifier may be thehumidity of air immediately surrounding the humidifier, e.g. thehumidity in the room where a patient is sleeping. Such ambient humiditymay be different to the humidity outside the room where a patient issleeping.

In another example, ambient pressure may be the pressure immediatelysurrounding or external to the body.

In certain forms, ambient (e.g., acoustic) noise may be considered to bethe background noise level in the room where a patient is located, otherthan for example, noise generated by an RPT device or emanating from amask or patient interface. Ambient noise may be generated by sourcesoutside the room.

Automatic Positive Airway Pressure (APAP) therapy: CPAP therapy in whichthe treatment pressure is automatically adjustable, e.g. from breath tobreath, between minimum and maximum limits, depending on the presence orabsence of indications of SDB events.

Continuous Positive Airway Pressure (CPAP) therapy: Respiratory pressuretherapy in which the treatment pressure is approximately constantthrough a respiratory cycle of a patient. In some forms, the pressure atthe entrance to the airways will be slightly higher during exhalation,and slightly lower during inhalation. In some forms, the pressure willvary between different respiratory cycles of the patient, for example,being increased in response to detection of indications of partial upperairway obstruction, and decreased in the absence of indications ofpartial upper airway obstruction.

Flow rate: The volume (or mass) of air delivered per unit time. Flowrate may refer to an instantaneous quantity. In some cases, a referenceto flow rate will be a reference to a scalar quantity, namely a quantityhaving magnitude only. In other cases, a reference to flow rate will bea reference to a vector quantity, namely a quantity having bothmagnitude and direction. Flow rate may be given the symbol Q. ‘Flowrate’ is sometimes shortened to simply ‘flow’.

In the example of patient respiration, a flow rate may be nominallypositive for the inspiratory portion of a breathing cycle of a patient,and hence negative for the expiratory portion of the breathing cycle ofa patient. Total flow rate, Qt, is the flow rate of air leaving the RPTdevice. Vent flow rate, Qv, is the flow rate of air leaving a vent toallow washout of exhaled gases. Leak flow rate, Ql, is the flow rate ofleak from a patient interface system or elsewhere. Respiratory flowrate, Qr, is the flow rate of air that is received into the patient'srespiratory system.

Humidifier: The word humidifier will be taken to mean a humidifyingapparatus constructed and arranged, or configured with a physicalstructure to be capable of providing a therapeutically beneficial amountof water (H20) vapour to a flow of air to ameliorate a medicalrespiratory condition of a patient.

Leak: The word leak will be taken to be an unintended flow of air. Inone example, leak may occur as the result of an incomplete seal betweena mask and a patient's face. In another example leak may occur in aswivel elbow to the ambient.

Noise, conducted (acoustic): Conducted noise in the present documentrefers to noise which is carried to the patient by the pneumatic path,such as the air circuit and the patient interface as well as the airtherein. In one form, conducted noise may be quantified by measuringsound pressure levels at the end of an air circuit.

Noise, radiated (acoustic): Radiated noise in the present documentrefers to noise which is carried to the patient by the ambient air. Inone form, radiated noise may be quantified by measuring soundpower/pressure levels of the object in question according to ISO 3744.

Noise, vent (acoustic): Vent noise in the present document refers tonoise which is generated by the flow of air through any vents such asvent holes of the patient interface.

Patient: A person, whether or not they are suffering from a respiratorycondition.

Pressure: Force per unit area. Pressure may be expressed in a range ofunits, including cmH₂O, g-f/cm² and hectopascal. 1 cmH₂O is equal to 1g-f/cm² and is approximately 0.98 hectopascal. In this specification,unless otherwise stated, pressure is given in units of cmH₂O.

The pressure in the patient interface is given the symbol Pm, while thetreatment pressure, which represents a target value to be achieved bythe mask pressure Pm at the current instant of time, is given the symbolPt.

Respiratory Pressure Therapy (RPT): The application of a supply of airto an entrance to the airways at a treatment pressure that is typicallypositive with respect to atmosphere.

Ventilator: A mechanical device that provides pressure support to apatient to perform some or all of the work of breathing.

4.7.1.1 Materials

Silicone or Silicone Elastomer: A synthetic rubber. In thisspecification, a reference to silicone is a reference to liquid siliconerubber (LSR) or a compression moulded silicone rubber (CMSR). One formof commercially available LSR is SILASTIC (included in the range ofproducts sold under this trademark), manufactured by Dow Corning.Another manufacturer of LSR is Wacker. Unless otherwise specified to thecontrary, an exemplary form of LSR has a Shore A (or Type A) indentationhardness in the range of about 35 to about 45 as measured using ASTMD2240.

Polycarbonate: a thermoplastic polymer of Bisphenol-A Carbonate.

4.7.1.2 Mechanical Properties

Resilience: Ability of a material to absorb energy when deformedelastically and to release the energy upon unloading.

Resilient: Will release substantially all of the energy when unloaded.Includes e.g. certain silicones, and thermoplastic elastomers.

Hardness: The ability of a material per se to resist deformation (e.g.described by a Young's Modulus, or an indentation hardness scalemeasured on a standardised sample size).

-   -   ‘Soft’ materials may include silicone or thermo-plastic        elastomer (TPE), and may, e.g. readily deform under finger        pressure.    -   ‘Hard’ materials may include polycarbonate, polypropylene, steel        or aluminium, and may not e.g. readily deform under finger        pressure.

Stiffness (or rigidity) of a structure or component: The ability of thestructure or component to resist deformation in response to an appliedload. The load may be a force or a moment, e.g. compression, tension,bending or torsion. The structure or component may offer differentresistances in different directions.

Floppy structure or component: A structure or component that will changeshape, e.g. bend, when caused to support its own weight, within arelatively short period of time such as 1 second.

Rigid structure or component: A structure or component that will notsubstantially change shape when subject to the loads typicallyencountered in use. An example of such a use may be setting up andmaintaining a patient interface in sealing relationship with an entranceto a patient's airways, e.g. at a load of approximately 20 to 30 cmH₂Opressure.

As an example, an I-beam may comprise a different bending stiffness(resistance to a bending load) in a first direction in comparison to asecond, orthogonal direction. In another example, a structure orcomponent may be floppy in a first direction and rigid in a seconddirection.

4.7.2 Respiratory Cycle

Apnea: According to some definitions, an apnea is said to have occurredwhen flow falls below a predetermined threshold for a duration, e.g. 10seconds. An obstructive apnea will be said to have occurred when,despite patient effort, some obstruction of the airway does not allowair to flow. A central apnea will be said to have occurred when an apneais detected that is due to a reduction in breathing effort, or theabsence of breathing effort, despite the airway being patent. A mixedapnea occurs when a reduction or absence of breathing effort coincideswith an obstructed airway.

Breathing rate: The rate of spontaneous respiration of a patient,usually measured in breaths per minute.

Duty cycle: The ratio of inhalation time, Ti to total breath time, Ttot.

Effort (breathing): The work done by a spontaneously breathing personattempting to breathe.

Expiratory portion of a breathing cycle: The period from the start ofexpiratory flow to the start of inspiratory flow.

Flow limitation: Flow limitation will be taken to be the state ofaffairs in a patient's respiration where an increase in effort by thepatient does not give rise to a corresponding increase in flow. Whereflow limitation occurs during an inspiratory portion of the breathingcycle it may be described as inspiratory flow limitation. Where flowlimitation occurs during an expiratory portion of the breathing cycle itmay be described as expiratory flow limitation.

Types of flow limited inspiratory waveforms:

(i) Flattened: Having a rise followed by a relatively flat portion,followed by a fall.

(ii) M-shaped: Having two local peaks, one at the leading edge, and oneat the trailing edge, and a relatively flat portion between the twopeaks.

(iii) Chair-shaped: Having a single local peak, the peak being at theleading edge, followed by a relatively flat portion.

(iv) Reverse-chair shaped: Having a relatively flat portion followed bysingle local peak, the peak being at the trailing edge.

Hypopnea: According to some definitions, a hypopnea is taken to be areduction in flow, but not a cessation of flow. In one form, a hypopneamay be said to have occurred when there is a reduction in flow below athreshold rate for a duration. A central hypopnea will be said to haveoccurred when a hypopnea is detected that is due to a reduction inbreathing effort. In one form in adults, either of the following may beregarded as being hypopneas:

-   -   (i) a 30% reduction in patient breathing for at least 10 seconds        plus an associated 4% desaturation; or    -   (ii) a reduction in patient breathing (but less than 50%) for at        least 10 seconds, with an associated desaturation of at least 3%        or an arousal.

Hyperpnea: An increase in flow to a level higher than normal.

Inspiratory portion of a breathing cycle: The period from the start ofinspiratory flow to the start of expiratory flow will be taken to be theinspiratory portion of a breathing cycle.

Patency (airway): The degree of the airway being open, or the extent towhich the airway is open. A patent airway is open. Airway patency may bequantified, for example with a value of one (1) being patent, and avalue of zero (0), being closed (obstructed).

Positive End-Expiratory Pressure (PEEP): The pressure above atmospherein the lungs that exists at the end of expiration.

Peak flow rate (Qpeak): The maximum value of flow rate during theinspiratory portion of the respiratory flow waveform.

Respiratory flow rate, patient airflow rate, respiratory airflow rate(Qr): These terms may be understood to refer to the RPT device'sestimate of respiratory airflow rate, as opposed to “true respiratoryflow rate” or “true respiratory airflow rate”, which is the actualrespiratory flow rate experienced by the patient, usually expressed inlitres per minute.

Tidal volume (Vt): The volume of air inhaled or exhaled during normalbreathing, when extra effort is not applied.

(inhalation) Time (Ti): The duration of the inspiratory portion of therespiratory flow rate waveform.

(exhalation) Time (Te): The duration of the expiratory portion of therespiratory flow rate waveform.

(total) Time (Ttot): The total duration between the start of oneinspiratory portion of a respiratory flow rate waveform and the start ofthe following inspiratory portion of the respiratory flow rate waveform.

Typical recent ventilation: The value of ventilation around which recentvalues of ventilation Vent over some predetermined timescale tend tocluster, that is, a measure of the central tendency of the recent valuesof ventilation.

Upper airway obstruction (UAO): includes both partial and total upperairway obstruction. This may be associated with a state of flowlimitation, in which the flow rate increases only slightly or may evendecrease as the pressure difference across the upper airway increases(Starling resistor behaviour).

Ventilation (Vent): A measure of a rate of gas being exchanged by thepatient's respiratory system. Measures of ventilation may include one orboth of inspiratory and expiratory flow, per unit time. When expressedas a volume per minute, this quantity is often referred to as “minuteventilation”. Minute ventilation is sometimes given simply as a volume,understood to be the volume per minute.

4.7.3 Ventilation

Adaptive Servo-Ventilator (ASV): A servo-ventilator that has achangeable, rather than fixed target ventilation. The changeable targetventilation may be learned from some characteristic of the patient, forexample, a respiratory characteristic of the patient.

Backup rate: A parameter of a ventilator that establishes the minimumbreathing rate (typically in number of breaths per minute) that theventilator will deliver to the patient, if not triggered by spontaneousrespiratory effort.

Cycled: The termination of a ventilator's inspiratory phase. When aventilator delivers a breath to a spontaneously breathing patient, atthe end of the inspiratory portion of the breathing cycle, theventilator is said to be cycled to stop delivering the breath.

Expiratory positive airway pressure (EPAP): a base pressure, to which apressure varying within the breath is added to produce the desired maskpressure which the ventilator will attempt to achieve at a given time.

End expiratory pressure (EEP): Desired mask pressure which theventilator will attempt to achieve at the end of the expiratory portionof the breath. If the pressure waveform template Π(Φ) is zero-valued atthe end of expiration, i.e. Π(Φ)=0 when Φ=1, the EEP is equal to theEPAP.

Inspiratory positive airway pressure (IPAP): Maximum desired maskpressure which the ventilator will attempt to achieve during theinspiratory portion of the breath.

Pressure support: A number that is indicative of the increase inpressure during ventilator inspiration over that during ventilatorexpiration, and generally means the difference in pressure between themaximum value during inspiration and the base pressure (e.g.,PS=IPAP−EPAP). In some contexts pressure support means the differencewhich the ventilator aims to achieve, rather than what it actuallyachieves.

Servo-ventilator: A ventilator that measures patient ventilation, has atarget ventilation, and which adjusts the level of pressure support tobring the patient ventilation towards the target ventilation.

Spontaneous/Timed (S/T): A mode of a ventilator or other device thatattempts to detect the initiation of a breath of a spontaneouslybreathing patient. If however, the device is unable to detect a breathwithin a predetermined period of time, the device will automaticallyinitiate delivery of the breath.

Swing: Equivalent term to pressure support.

Triggered: When a ventilator delivers a breath of air to a spontaneouslybreathing patient, it is said to be triggered to do so at the initiationof the respiratory portion of the breathing cycle by the patient'sefforts.

Typical recent ventilation: The typical recent ventilation Vtyp is thevalue around which recent measures of ventilation over somepredetermined timescale tend to cluster. For example, a measure of thecentral tendency of the measures of ventilation over recent history maybe a suitable value of a typical recent ventilation.

4.7.4 Anatomy

4.7.4.1 Anatomy of the Face

Ala: the external outer wall or “wing” of each nostril (plural: alar)

Alare: The most lateral point on the nasal ala.

Alar curvature (or alar crest) point: The most posterior point in thecurved base line of each ala, found in the crease formed by the union ofthe ala with the cheek.

Auricle: The whole external visible part of the ear.

(nose) Bony framework: The bony framework of the nose comprises thenasal bones, the frontal process of the maxillae and the nasal part ofthe frontal bone.

(nose) Cartilaginous framework: The cartilaginous framework of the nosecomprises the septal, lateral, major and minor cartilages.

Columella: the strip of skin that separates the nares and which runsfrom the pronasale to the upper lip.

Columella angle: The angle between the line drawn through the midpointof the nostril aperture and a line drawn perpendicular to the Frankforthorizontal while intersecting subnasale.

Frankfort horizontal plane: A line extending from the most inferiorpoint of the orbital margin to the left tragion. The tragion is thedeepest point in the notch superior to the tragus of the auricle.

Glabella: Located on the soft tissue, the most prominent point in themidsagittal plane of the forehead.

Lateral nasal cartilage: A generally triangular plate of cartilage. Itssuperior margin is attached to the nasal bone and frontal process of themaxilla, and its inferior margin is connected to the greater alarcartilage.

Greater alar cartilage: A plate of cartilage lying below the lateralnasal cartilage. It is curved around the anterior part of the naris. Itsposterior end is connected to the frontal process of the maxilla by atough fibrous membrane containing three or four minor cartilages of theala.

Nares (Nostrils): Approximately ellipsoidal apertures forming theentrance to the nasal cavity. The singular form of nares is naris(nostril). The nares are separated by the nasal septum.

Naso-labial sulcus or Naso-labial fold: The skin fold or groove thatruns from each side of the nose to the corners of the mouth, separatingthe cheeks from the upper lip.

Naso-labial angle: The angle between the columella and the upper lip,while intersecting subnasale.

Otobasion inferior: The lowest point of attachment of the auricle to theskin of the face.

Otobasion superior: The highest point of attachment of the auricle tothe skin of the face.

Pronasale: the most protruded point or tip of the nose, which can beidentified in lateral view of the rest of the portion of the head.

Philtrum: the midline groove that runs from lower border of the nasalseptum to the top of the lip in the upper lip region.

Pogonion: Located on the soft tissue, the most anterior midpoint of thechin.

Ridge (nasal): The nasal ridge is the midline prominence of the nose,extending from the Sellion to the Pronasale.

Sagittal plane: A vertical plane that passes from anterior (front) toposterior (rear) dividing the body into right and left halves.

Sellion: Located on the soft tissue, the most concave point overlyingthe area of the frontonasal suture.

Septal cartilage (nasal): The nasal septal cartilage forms part of theseptum and divides the front part of the nasal cavity.

Subalare: The point at the lower margin of the alar base, where the alarbase joins with the skin of the superior (upper) lip.

Subnasal point: Located on the soft tissue, the point at which thecolumella merges with the upper lip in the midsagittal plane.

Supramentale: The point of greatest concavity in the midline of thelower lip between labrale inferius and soft tissue pogonion

4.7.4.2 Anatomy of the Skull

Frontal bone: The frontal bone includes a large vertical portion, thesquama frontalis, corresponding to the region known as the forehead.

Mandible: The mandible forms the lower jaw. The mental protuberance isthe bony protuberance of the jaw that forms the chin.

Maxilla: The maxilla forms the upper jaw and is located above themandible and below the orbits. The frontal process of the maxillaprojects upwards by the side of the nose, and forms part of its lateralboundary.

Nasal bones: The nasal bones are two small oblong bones, varying in sizeand form in different individuals; they are placed side by side at themiddle and upper part of the face, and form, by their junction, the“bridge” of the nose.

Nasion: The intersection of the frontal bone and the two nasal bones, adepressed area directly between the eyes and superior to the bridge ofthe nose.

Occipital bone: The occipital bone is situated at the back and lowerpart of the cranium. It includes an oval aperture, the foramen magnum,through which the cranial cavity communicates with the vertebral canal.The curved plate behind the foramen magnum is the squama occipitalis.

Orbit: The bony cavity in the skull to contain the eyeball.

Parietal bones: The parietal bones are the bones that, when joinedtogether, form the roof and sides of the cranium.

Temporal bones: The temporal bones are situated on the bases and sidesof the skull, and support that part of the face known as the temple.

Zygomatic bones: The face includes two zygomatic bones, located in theupper and lateral parts of the face and forming the prominence of thecheek.

4.7.4.3 Anatomy of the Respiratory System

Diaphragm: A sheet of muscle that extends across the bottom of the ribcage. The diaphragm separates the thoracic cavity, containing the heart,lungs and ribs, from the abdominal cavity. As the diaphragm contractsthe volume of the thoracic cavity increases and air is drawn into thelungs.

Larynx: The larynx, or voice box houses the vocal folds and connects theinferior part of the pharynx (hypopharynx) with the trachea.

Lungs: The organs of respiration in humans. The conducting zone of thelungs contains the trachea, the bronchi, the bronchioles, and theterminal bronchioles. The respiratory zone contains the respiratorybronchioles, the alveolar ducts, and the alveoli.

Nasal cavity: The nasal cavity (or nasal fossa) is a large air filledspace above and behind the nose in the middle of the face. The nasalcavity is divided in two by a vertical fin called the nasal septum. Onthe sides of the nasal cavity are three horizontal outgrowths callednasal conchae (singular “concha”) or turbinates. To the front of thenasal cavity is the nose, while the back blends, via the choanae, intothe nasopharynx.

Pharynx: The part of the throat situated immediately inferior to (below)the nasal cavity, and superior to the oesophagus and larynx. The pharynxis conventionally divided into three sections: the nasopharynx(epipharynx) (the nasal part of the pharynx), the oropharynx(mesopharynx) (the oral part of the pharynx), and the laryngopharynx(hypopharynx).

4.7.5 Patient Interface

Anti-asphyxia valve (AAV): The component or sub-assembly of a masksystem that, by opening to atmosphere in a failsafe manner, reduces therisk of excessive CO₂ rebreathing by a patient.

Elbow: An elbow is an example of a structure that directs an axis offlow of air travelling therethrough to change direction through anangle. In one form, the angle may be approximately 90 degrees. Inanother form, the angle may be more, or less than 90 degrees. The elbowmay have an approximately circular cross-section. In another form theelbow may have an oval or a rectangular cross-section. In certain formsan elbow may be rotatable with respect to a mating component, e.g. about360 degrees. In certain forms an elbow may be removable from a matingcomponent, e.g. via a snap connection. In certain forms, an elbow may beassembled to a mating component via a one-time snap during manufacture,but not removable by a patient.

Frame: Frame will be taken to mean a mask structure that bears the loadof tension between two or more points of connection with a headgear. Amask frame may be a non-airtight load bearing structure in the mask.However, some forms of mask frame may also be air-tight.

Headgear: Headgear will be taken to mean a form of positioning andstabilizing structure designed for use on a head. For example, theheadgear may comprise a collection of one or more struts, ties andstiffeners configured to locate and retain a patient interface inposition on a patient's face for delivery of respiratory therapy. Someties are formed of a soft, flexible, elastic material such as alaminated composite of foam and fabric.

Membrane: Membrane will be taken to mean a typically thin element thathas, preferably, substantially no resistance to bending, but hasresistance to being stretched.

Plenum chamber: a mask plenum chamber will be taken to mean a portion ofa patient interface having walls at least partially enclosing a volumeof space, the volume having air therein pressurised above atmosphericpressure in use. A shell may form part of the walls of a mask plenumchamber.

Seal: May be a noun form (“a seal”) which refers to a structure, or averb form (“to seal”) which refers to the effect. Two elements may beconstructed and/or arranged to ‘seal’ or to effect ‘sealing’therebetween without requiring a separate ‘seal’ element per se.

Shell: A shell will be taken to mean a curved, relatively thin structurehaving bending, tensile and compressive stiffness. For example, a curvedstructural wall of a mask may be a shell. In some forms, a shell may befaceted. In some forms a shell may be airtight. In some forms a shellmay not be airtight.

Stiffener: A stiffener will be taken to mean a structural componentdesigned to increase the bending resistance of another component in atleast one direction.

Strut: A strut will be taken to be a structural component designed toincrease the compression resistance of another component in at least onedirection.

Swivel (noun): A subassembly of components configured to rotate about acommon axis, preferably independently, preferably under low torque. Inone form, the swivel may be constructed to rotate through an angle of atleast 360 degrees. In another form, the swivel may be constructed torotate through an angle less than 360 degrees. When used in the contextof an air delivery conduit, the sub-assembly of components preferablycomprises a matched pair of cylindrical conduits. There may be little orno leak flow of air from the swivel in use.

Tie (noun): A structure designed to resist tension.

Vent: (noun): A structure that allows a flow of air from an interior ofthe mask, or conduit, to ambient air for clinically effective washout ofexhaled gases. For example, a clinically effective washout may involve aflow rate of about 10 litres per minute to about 100 litres per minute,depending on the mask design and treatment pressure.

4.7.6 Shape of Structures

Products in accordance with the present technology may comprise one ormore three-dimensional mechanical structures, for example a mask cushionor an impeller. The three-dimensional structures may be bounded bytwo-dimensional surfaces. These surfaces may be distinguished using alabel to describe an associated surface orientation, location, function,or some other characteristic. For example a structure may comprise oneor more of an anterior surface, a posterior surface, an interior surfaceand an exterior surface. In another example, a cushion structure maycomprise a face-contacting (e.g. outer) surface, and a separatenon-face-contacting (e.g. underside or inner) surface. In anotherexample, a structure may comprise a first surface and a second surface.

To facilitate describing the shape of the three-dimensional structuresand the surfaces, we first consider a cross-section through a surface ofthe structure at a point, p. See FIG. 3B to FIG. 3F, which illustrateexamples of cross-sections at point p on a surface, and the resultingplane curves. FIGS. 3B to 3F also illustrate an outward normal vector atp. The outward normal vector at p points away from the surface. In someexamples we describe the surface from the point of view of an imaginarysmall person standing upright on the surface.

4.7.6.1 Curvature in One Dimension

The curvature of a plane curve at p may be described as having a sign(e.g. positive, negative) and a magnitude (e.g. 1/radius of a circlethat just touches the curve at p).

Positive curvature: If the curve at p turns towards the outward normal,the curvature at that point will be taken to be positive (if theimaginary small person leaves the point p they must walk uphill). SeeFIG. 3B (relatively large positive curvature compared to FIG. 3C) andFIG. 3C (relatively small positive curvature compared to FIG. 3B). Suchcurves are often referred to as concave.

Zero curvature: If the curve at p is a straight line, the curvature willbe taken to be zero (if the imaginary small person leaves the point p,they can walk on a level, neither up nor down). See FIG. 3D.

Negative curvature: If the curve at p turns away from the outwardnormal, the curvature in that direction at that point will be taken tobe negative (if the imaginary small person leaves the point p they mustwalk downhill). See FIG. 3E (relatively small negative curvaturecompared to FIG. 3F) and FIG. 3F (relatively large negative curvaturecompared to FIG. 3E). Such curves are often referred to as convex.

4.7.6.2 Curvature of Two Dimensional Surfaces

A description of the shape at a given point on a two-dimensional surfacein accordance with the present technology may include multiple normalcross-sections. The multiple cross-sections may cut the surface in aplane that includes the outward normal (a “normal plane”), and eachcross-section may be taken in a different direction. Each cross-sectionresults in a plane curve with a corresponding curvature. The differentcurvatures at that point may have the same sign, or a different sign.Each of the curvatures at that point has a magnitude, e.g. relativelysmall. The plane curves in FIGS. 3B to 3F could be examples of suchmultiple cross-sections at a particular point.

Principal curvatures and directions: The directions of the normal planeswhere the curvature of the curve takes its maximum and minimum valuesare called the principal directions. In the examples of FIG. 3B to FIG.3F, the maximum curvature occurs in FIG. 3B, and the minimum occurs inFIG. 3F, hence FIG. 3B and FIG. 3F are cross sections in the principaldirections. The principal curvatures at p are the curvatures in theprincipal directions.

Region of a surface: A connected set of points on a surface. The set ofpoints in a region may have similar characteristics, e.g. curvatures orsigns.

Saddle region: A region where at each point, the principal curvatureshave opposite signs, that is, one is positive, and the other is negative(depending on the direction to which the imaginary person turns, theymay walk uphill or downhill).

Dome region: A region where at each point the principal curvatures havethe same sign, e.g. both positive (a “concave dome”) or both negative (a“convex dome”).

Cylindrical region: A region where one principal curvature is zero (or,for example, zero within manufacturing tolerances) and the otherprincipal curvature is non-zero.

Planar region: A region of a surface where both of the principalcurvatures are zero (or, for example, zero within manufacturingtolerances).

Edge of a surface: A boundary or limit of a surface or region.

Path: In certain forms of the present technology, ‘path’ will be takento mean a path in the mathematical—topological sense, e.g. a continuousspace curve from f(0) to f(1) on a surface. In certain forms of thepresent technology, a ‘path’ may be described as a route or course,including e.g. a set of points on a surface. (The path for the imaginaryperson is where they walk on the surface, and is analogous to a gardenpath).

Path length: In certain forms of the present technology, ‘path length’will be taken to mean the distance along the surface from f(0) to f(1),that is, the distance along the path on the surface. There may be morethan one path between two points on a surface and such paths may havedifferent path lengths. (The path length for the imaginary person wouldbe the distance they have to walk on the surface along the path).

Straight-line distance: The straight-line distance is the distancebetween two points on a surface, but without regard to the surface. Onplanar regions, there would be a path on the surface having the samepath length as the straight-line distance between two points on thesurface. On non-planar surfaces, there may be no paths having the samepath length as the straight-line distance between two points. (For theimaginary person, the straight-line distance would correspond to thedistance ‘as the crow flies’.)

4.7.6.3 Space Curves

Space curves: Unlike a plane curve, a space curve does not necessarilylie in any particular plane. A space curve may be considered to be aone-dimensional piece of three-dimensional space. An imaginary personwalking on a strand of the DNA helix walks along a space curve. Atypical human left ear comprises a helix, which is a left-hand helix,see FIG. 3Q. A typical human right ear comprises a helix, which is aright-hand helix, see FIG. 3R. FIG. 3S shows a right-hand helix. Theedge of a structure, e.g. the edge of a membrane or impeller, may followa space curve. In general, a space curve may be described by a curvatureand a torsion at each point on the space curve. Torsion is a measure ofhow the curve turns out of a plane. Torsion has a sign and a magnitude.The torsion at a point on a space curve may be characterised withreference to the tangent, normal and binormal vectors at that point.

Tangent unit vector (or unit tangent vector): For each point on a curve,a vector at the point specifies a direction from that point, as well asa magnitude. A tangent unit vector is a unit vector pointing in the samedirection as the curve at that point. If an imaginary person were flyingalong the curve and fell off her vehicle at a particular point, thedirection of the tangent vector is the direction she would betravelling.

Unit normal vector: As the imaginary person moves along the curve, thistangent vector itself changes. The unit vector pointing in the samedirection that the tangent vector is changing is called the unitprincipal normal vector. It is perpendicular to the tangent vector.

Binormal unit vector: The binormal unit vector is perpendicular to boththe tangent vector and the principal normal vector. Its direction may bedetermined by a right-hand rule (see e.g. FIG. 3P), or alternatively bya left-hand rule (FIG. 3O).

Osculating plane: The plane containing the unit tangent vector and theunit principal normal vector. See FIGS. 3O and 3P.

Torsion of a space curve: The torsion at a point of a space curve is themagnitude of the rate of change of the binormal unit vector at thatpoint. It measures how much the curve deviates from the osculatingplane. A space curve which lies in a plane has zero torsion. A spacecurve which deviates a relatively small amount from the osculating planewill have a relatively small magnitude of torsion (e.g. a gently slopinghelical path). A space curve which deviates a relatively large amountfrom the osculating plane will have a relatively large magnitude oftorsion (e.g. a steeply sloping helical path). With reference to FIG.3S, since T2>T1, the magnitude of the torsion near the top coils of thehelix of FIG. 3S is greater than the magnitude of the torsion of thebottom coils of the helix of FIG. 3S

With reference to the right-hand rule of FIG. 3P, a space curve turningtowards the direction of the right-hand binormal may be considered ashaving a right-hand positive torsion (e.g. a right-hand helix as shownin FIG. 3S). A space curve turning away from the direction of theright-hand binormal may be considered as having a right-hand negativetorsion (e.g. a left-hand helix).

Equivalently, and with reference to a left-hand rule (see FIG. 3O), aspace curve turning towards the direction of the left-hand binormal maybe considered as having a left-hand positive torsion (e.g. a left-handhelix). Hence left-hand positive is equivalent to right-hand negative.See FIG. 3T.

4.7.6.4 Holes

A surface may have a one-dimensional hole, e.g. a hole bounded by aplane curve or by a space curve. Thin structures (e.g. a membrane) witha hole, may be described as having a one-dimensional hole. See forexample the one dimensional hole in the surface of structure shown inFIG. 3I, bounded by a plane curve.

A structure may have a two-dimensional hole, e.g. a hole bounded by asurface. For example, an inflatable tyre has a two dimensional holebounded by the interior surface of the tyre. In another example, abladder with a cavity for air or gel could have a two-dimensional hole.See for example the cushion of FIG. 3L and the example cross-sectionstherethrough in FIG. 3M and FIG. 3N, with the interior surface boundinga two dimensional hole indicated. In a yet another example, a conduitmay comprise a one-dimension hole (e.g. at its entrance or at its exit),and a two-dimension hole bounded by the inside surface of the conduit.See also the two dimensional hole through the structure shown in FIG.3K, bounded by a surface as shown.

4.8 OTHER REMARKS

A portion of the disclosure of this patent document contains materialwhich is subject to copyright protection. The copyright owner has noobjection to the facsimile reproduction by anyone of the patent documentor the patent disclosure, as it appears in Patent Office patent files orrecords, but otherwise reserves all copyright rights whatsoever.

Unless the context clearly dictates otherwise and where a range ofvalues is provided, it is understood that each intervening value, to thetenth of the unit of the lower limit, between the upper and lower limitof that range, and any other stated or intervening value in that statedrange is encompassed within the technology. The upper and lower limitsof these intervening ranges, which may be independently included in theintervening ranges, are also encompassed within the technology, subjectto any specifically excluded limit in the stated range. Where the statedrange includes one or both of the limits, ranges excluding either orboth of those included limits are also included in the technology.

Furthermore, where a value or values are stated herein as beingimplemented as part of the technology, it is understood that such valuesmay be approximated, unless otherwise stated, and such values may beutilized to any suitable significant digit to the extent that apractical technical implementation may permit or require it.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this technology belongs. Although any methods andmaterials similar or equivalent to those described herein can also beused in the practice or testing of the present technology, a limitednumber of the exemplary methods and materials are described herein.

When a particular material is identified as being used to construct acomponent, obvious alternative materials with similar properties may beused as a substitute. Furthermore, unless specified to the contrary, anyand all components herein described are understood to be capable ofbeing manufactured and, as such, may be manufactured together orseparately.

It must be noted that as used herein and in the appended claims, thesingular forms “a”, “an”, and “the” include their plural equivalents,unless the context clearly dictates otherwise.

All publications mentioned herein are incorporated herein by referencein their entirety to disclose and describe the methods and/or materialswhich are the subject of those publications. The publications discussedherein are provided solely for their disclosure prior to the filing dateof the present application. Nothing herein is to be construed as anadmission that the present technology is not entitled to antedate suchpublication by virtue of prior invention. Further, the dates ofpublication provided may be different from the actual publication dates,which may need to be independently confirmed.

The terms “comprises” and “comprising” should be interpreted asreferring to elements, components, or steps in a non-exclusive manner,indicating that the referenced elements, components, or steps may bepresent, or utilized, or combined with other elements, components, orsteps that are not expressly referenced.

The subject headings used in the detailed description are included onlyfor the ease of reference of the reader and should not be used to limitthe subject matter found throughout the disclosure or the claims. Thesubject headings should not be used in construing the scope of theclaims or the claim limitations.

Although the technology herein has been described with reference toparticular examples, it is to be understood that these examples aremerely illustrative of the principles and applications of thetechnology. In some instances, the terminology and symbols may implyspecific details that are not required to practice the technology. Forexample, although the terms “first” and “second” may be used, unlessotherwise specified, they are not intended to indicate any order but maybe utilised to distinguish between distinct elements. Furthermore,although process steps in the methodologies may be described orillustrated in an order, such an ordering is not required. Those skilledin the art will recognize that such ordering may be modified and/oraspects thereof may be conducted concurrently or even synchronously.

It is therefore to be understood that numerous modifications may be madeto the illustrative examples and that other arrangements may be devisedwithout departing from the spirit and scope of the technology.

4.9 REFERENCE SIGNS LIST

-   1000 patient-   1100 bed partner-   3000 patient interface-   3100 seal-forming structure-   3105 sealing surface-   3110 tie-   3111 end-   3115 outer perimeter-   3120 tube-shaped structure-   3125 sealing flap-   3130 thick portion-   3135 thin portion-   3140 hinge structure-   3145 attachment portion-   3150 flap-   3155 rib-   3160 flap-   3165 connection point-   3170 angle-   3175 region-   3175A region-   3175B region-   3175C region-   3175D region-   3175E region-   3175F region-   3180A region-   3180B region-   3180C region-   3180D region-   3180E region-   3180F region-   3180G region-   3180H region-   3185 sagittal plane-   3190 line-   3195 first tangent-   3196 second tangent-   3197 central opening-   3198A region-   3198B region-   3199A closed path-   3199B open path-   3200 plenum chamber-   3210 perimeter-   3220 marginal edge-   3300 structure-   3400 vent-   3600 connection port-   3700 forehead support-   3800 cushion assembly-   3810 cushion-   3810 foam cushion-   3812 flexible supporting clip-   3814 second clip-   3816 mask shell-   4000 RPT device-   4170 air circuit-   5000 humidifier-   6000 structure-   6005 region-   6005A region-   6005B region-   6005C region-   6005D region-   6005F region-   6005G region

The invention claimed is:
 1. A cushion assembly for a patient interfacefor sealed delivery of a flow of air at a continuously positive pressurewith respect to ambient air pressure to an entrance to a patient'sairways including at least entrance of the patient's nares, wherein thepatient interface is configured to maintain a therapy pressure in arange of about 4 cmH2O to about 30 cmH2O above ambient air pressure inuse, throughout the patient's respiratory cycle, while the patient issleeping, to ameliorate sleep disordered breathing, the cushion assemblycomprising: an elastomeric seal-forming portion shaped to be bisected bya sagittal plane that includes a line tangent to the elastomericseal-forming portion at a superior tangent point and an inferior tangentpoint, wherein the elastomeric seal-forming portion comprises: adome-shaped superior region that straddles the sagittal plane in thevicinity of the superior tangent point, a saddle-shaped inferior regionthat straddles the sagittal plane and includes the inferior tangentpoint, a first support region extending from the saddle-shaped inferiorregion to the dome-shaped superior region, the first support regionhaving a consistent elastomeric wall thickness that is greater than anelastomeric wall thickness of the dome-shaped superior region and thesaddle-shaped inferior region, and a second support region adjacent thefirst support region that extends from the saddle-shaped inferior regionto the dome-shaped superior region, the second support region beingbounded by the first support region on a proximal side and having adistal side opposite the proximal side, an elastomeric wall thickness inthe second support region increases from the distal side to the proximalside.
 2. The cushion assembly of claim 1, wherein the elastomeric wallthickness of the second support region at the distal side is less thanthe elastomeric wall thickness of the second support region at theproximal side.
 3. The cushion assembly of claim 1, wherein theelastomeric wall thickness of the second support region at the proximalside is the same as the elastomeric wall thickness of the first supportregion.
 4. The cushion assembly of claim 1, wherein the elastomericseal-forming portion further comprises a third support region adjacentthe second support region, the second support region being bounded bythe third support region at the distal side.
 5. The cushion assembly ofclaim 4, wherein an elastomeric wall thickness of the third supportregion is the same as the elastomeric wall thickness at the proximalside of the second support region.
 6. The cushion assembly of claim 1,wherein the elastomeric seal-forming portion further comprises asaddle-shaped superior region that straddles the sagittal plane in thevicinity of the superior tangent point.
 7. The cushion assembly of claim6, wherein an elastomeric wall thickness in the saddle-shaped superiorregion is less than the elastomeric wall thickness in the domes-shapedsuperior region.
 8. The cushion assembly of claim 6, wherein theelastomeric seal-forming portion further comprises a compliant regionbounded by the second support region, the saddle-shaped superior regionand the dome-shaped superior region.
 9. The cushion assembly of claim 8,wherein an elastomeric wall thickness in the compliant region is greaterthan the elastomeric wall thickness of the saddle-shaped superior regionand the elastomeric wall thickness of the dome-shaped superior region.10. The cushion assembly of claim 8, wherein an elastomeric wallthickness in the compliant region is less than the elastomeric wallthickness of the second support region.
 11. The cushion assembly ofclaim 8, wherein the elastomeric seal-forming portion further comprisesa loop connection extending from the compliant region and the secondsupport region.
 12. The cushion assembly of claim 11, wherein theelastomeric seal-forming portion further comprises a flap portionextending from the compliant region and the second support region. 13.The cushion assembly of claim 12, wherein the flap portion extends froma location where the loop connection is attached to the compliant regionand the second support region.
 14. The cushion assembly of claim 12,wherein an elastomeric wall thickness in the flap portion is less thanthe elastomeric wall thickness in the compliant region and the secondsupport region.
 15. The cushion assembly of claim 12, wherein the flapportion is configured to move independently of the loop connection. 16.A patient interface comprising: the cushion assembly of claim 1; a rigidshell removably connected to the cushion assembly; and headgearremovably attached to the rigid shell.
 17. A CPAP system comprising: thepatient interface according to claim 16; a flow generator configured topressurize a flow of gas; and an air delivery tube configured to deliverthe pressurized gas to the patient interface.
 18. The cushion assemblyof claim 1, wherein the elastomeric seal-forming portion is dome-shapedat the superior tangent point.
 19. A cushion assembly for a patientinterface for sealed delivery of a flow of air at a continuouslypositive pressure with respect to ambient air pressure to an entrance toa patient's airways including at least entrance of the patient's nares,wherein the patient interface is configured to maintain a therapypressure in a range of about 4 cmH2O to about 30 cmH2O above ambient airpressure in use, throughout the patient's respiratory cycle, while thepatient is sleeping, to ameliorate sleep disordered breathing, thecushion assembly comprising: an elastomeric seal-forming structureshaped to be bisected by a sagittal plane that includes a line tangentto the elastomeric seal-forming structure at a superior tangent pointand an inferior tangent point, the elastomeric seal-forming structurecomprising: a posterior central opening and an anterior central openingopposite the posterior central opening, the elastomeric seal-formingstructure including a plurality of closed paths concentric to theposterior central opening; a dome-shaped superior region that straddlesthe sagittal plane in the vicinity of the superior tangent point, thedome-shaped superior region being positioned on the outermost closedpath; a saddle-shaped superior region that straddles the sagittal planein the vicinity of the superior tangent point, the saddle-shapedsuperior region being positioned on the innermost closed path; asaddle-shaped inferior region that straddles the sagittal plane andincludes the inferior tangent point, the saddle-shaped inferior regionbeing on both the innermost closed path and the outermost closed path;wherein an elastomeric wall thickness of the elastomeric seal-formingstructure is invariable along a portion of the outermost closed pathextending from the saddle-shaped inferior region to the dome-shapedsuperior region; and wherein the elastomeric wall thickness of theelastomeric seal-forming structure varies along a portion of theinnermost closed path that extends from the saddle-shaped inferiorregion to the saddle-shaped superior region.
 20. The cushion assembly ofclaim 19, wherein the portion of the outermost closed path extendingfrom the saddle-shaped inferior region to the dome-shaped superiorregion includes a saddle-shaped portion.
 21. The cushion assembly ofclaim 19, wherein the portion of the outermost closed path extendingfrom the saddle-shaped inferior region to the dome-shaped superiorregion includes a dome-shaped portion.
 22. The cushion assembly of claim19, wherein the portion of the innermost closed path extending from thesaddle-shaped inferior region to the saddle-shaped superior regionincludes a saddle-shaped portion.
 23. The cushion assembly of claim 19,wherein the portion of the innermost closed path extending from thesaddle-shaped inferior region to the saddle-shaped superior regionincludes a dome-shaped portion.
 24. A patient interface comprising: thecushion assembly of claim 19; a rigid shell removably connected to thecushion assembly; and headgear removably attached to the rigid shell.25. A CPAP system comprising: the patient interface according to claim24; a flow generator configured to pressurize a flow of gas; and an airdelivery tube configured to deliver the pressurized gas to the patientinterface.
 26. A cushion assembly for a patient interface for sealeddelivery of a flow of air at a continuously positive pressure withrespect to ambient air pressure to an entrance to a patient's airwaysincluding at least entrance of the patient's nares, wherein the patientinterface is configured to maintain a therapy pressure in a range ofabout 4 cmH2O to about 30 cmH2O above ambient air pressure in use,throughout the patient's respiratory cycle, while the patient issleeping, to ameliorate sleep disordered breathing, the cushion assemblycomprising: an elastomeric seal-forming structure that is shaped to bebisected by a sagittal plane that has a line that is tangent to theelastomeric seal-forming structure at a superior tangent point and at aninferior tangent point, wherein a first nasal bridge region of theelastomeric seal-forming structure straddles the sagittal plane in thevicinity of the superior tangent point, wherein a second nasal bridgeregion of the elastomeric seal-forming structure straddles the sagittalplane in the vicinity of the superior tangent point and is configured toseal against the patient's nasal bridge when the cushion is mounted onthe patient's face, the second nasal bridge region having a thinnerelastomeric wall than the first nasal bridge region, wherein a chinregion of the elastomeric seal-forming structure straddles the sagittalplane and includes the inferior tangent point, the chin region beingconfigured to engage the patient's chin when the cushion is mounted onthe patient's face, the chin region having the same elastomeric wallthickness as the first nasal bridge region, wherein a first supportregion and a second support region are positioned side by side and bothextend from the chin region to the first nasal bridge region, the firstsupport region having a consistent elastomeric wall thickness, and thesecond support region having a varied elastomeric wall thickness. 27.The cushion assembly of claim 26, wherein the elastomeric wall thicknessof the second support region is consistent in the direction from thechin region to the first nasal bridge.
 28. The cushion assembly of claim26, wherein the elastomeric wall thickness in the second support regionincreases toward the first support region.
 29. The cushion assembly ofclaim 26, wherein the elastomeric seal-forming structure furthercomprises a compliant region configured to engage a side of the upperportion of the patient's nose, an elastomeric wall thickness in thecompliant region being less than the second support region and greaterthan the first nasal bridge region.
 30. The cushion assembly of claim29, wherein the compliant region is bounded by the first nasal bridgeregion, the second nasal bridge region and the second support region.31. The cushion assembly of claim 30, wherein the elastomericseal-forming structure further comprises a loop structure extending fromthe second support region and the compliant region.
 32. The cushionassembly of claim 31, wherein the elastomeric seal-forming structurefurther comprises a flap portion bounded by the second nasal bridgeregion, the compliant region and the second support region.
 33. Thecushion assembly of claim 32, wherein an elastomeric wall thickness ofthe flap portion is greater than the second nasal bridge region and lessthan the elastomeric wall thickness of the compliant region.
 34. Thecushion assembly of claim 32, wherein the flap portion is configured tomove independently of the loop structure.
 35. The cushion assembly ofclaim 26, wherein an elastomeric seal-forming structure furthercomprises a third support region bounded by the chin region, the secondsupport region and the flap portion.
 36. The cushion assembly of claim35, wherein an elastomeric wall thickness of the third support region isgreater than the elastomeric wall thickness in the chin region and isless than the elastomeric wall thickness in the first support region.37. A patient interface comprising: the cushion assembly of claim 26; arigid shell removably connected to the cushion assembly; and headgearremovably attached to the rigid shell.
 38. A CPAP system comprising: thepatient interface according to claim 37; a flow generator configured topressurize a flow of gas; and an air delivery tube configured to deliverthe pressurized gas to the patient interface.